diff --git a/DEPS b/DEPS
index d261291b265..068eb9618e2 100644
--- a/DEPS
+++ b/DEPS
@@ -479,7 +479,7 @@ deps = {
     "packages": [
       {
         "package": "dart/cfe/dart2js_dills",
-        "version": "binary_version:38",
+        "version": "binary_version:39",
       }
     ],
     "dep_type": "cipd",
diff --git a/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart b/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
index c6b8eb2417a..8ebde46009c 100644
--- a/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
@@ -119,11 +119,12 @@ class ConstructorBuilderImpl extends FunctionBuilderImpl
       Constructor referenceFrom,
       [String nativeMethodName])
       : _constructor = new Constructor(null,
-            fileUri: compilationUnit?.fileUri,
+            fileUri: compilationUnit.fileUri,
             reference: referenceFrom?.reference)
           ..startFileOffset = startCharOffset
           ..fileOffset = charOffset
-          ..fileEndOffset = charEndOffset,
+          ..fileEndOffset = charEndOffset
+          ..isNonNullableByDefault = compilationUnit.isNonNullableByDefault,
         super(metadata, modifiers, returnType, name, typeVariables, formals,
             compilationUnit, charOffset, nativeMethodName);
 
diff --git a/pkg/front_end/lib/src/fasta/builder/field_builder.dart b/pkg/front_end/lib/src/fasta/builder/field_builder.dart
index 6dbdd64ccdd..9f0ca67530e 100644
--- a/pkg/front_end/lib/src/fasta/builder/field_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/field_builder.dart
@@ -176,8 +176,8 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
       assert(lateIsSetReferenceFrom == null);
       assert(getterReferenceFrom == null);
       assert(setterReferenceFrom == null);
-      _fieldEncoding = new RegularFieldEncoding(
-          fileUri, charOffset, charEndOffset, reference);
+      _fieldEncoding = new RegularFieldEncoding(fileUri, charOffset,
+          charEndOffset, reference, library.isNonNullableByDefault);
     }
   }
 
@@ -511,11 +511,12 @@ abstract class FieldEncoding {
 class RegularFieldEncoding implements FieldEncoding {
   Field _field;
 
-  RegularFieldEncoding(
-      Uri fileUri, int charOffset, int charEndOffset, Field reference) {
+  RegularFieldEncoding(Uri fileUri, int charOffset, int charEndOffset,
+      Field reference, bool isNonNullableByDefault) {
     _field = new Field(null, fileUri: fileUri, reference: reference?.reference)
       ..fileOffset = charOffset
-      ..fileEndOffset = charEndOffset;
+      ..fileEndOffset = charEndOffset
+      ..isNonNullableByDefault = isNonNullableByDefault;
   }
 
   @override
@@ -645,15 +646,18 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
     _field =
         new Field(null, fileUri: fileUri, reference: referenceFrom?.reference)
           ..fileOffset = charOffset
-          ..fileEndOffset = charEndOffset;
+          ..fileEndOffset = charEndOffset
+          ..isNonNullableByDefault = true;
     _lateIsSetField = new Field(null,
         fileUri: fileUri, reference: lateIsSetReferenceFrom?.reference)
       ..fileOffset = charOffset
-      ..fileEndOffset = charEndOffset;
+      ..fileEndOffset = charEndOffset
+      ..isNonNullableByDefault = true;
     _lateGetter = new Procedure(
         null, ProcedureKind.Getter, new FunctionNode(null),
         fileUri: fileUri, reference: getterReferenceFrom?.reference)
-      ..fileOffset = charOffset;
+      ..fileOffset = charOffset
+      ..isNonNullableByDefault = true;
     _lateSetter = _createSetter(name, fileUri, charOffset, setterReferenceFrom);
   }
 
@@ -751,7 +755,8 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
             positionalParameters: [parameter], returnType: const VoidType()),
         fileUri: fileUri,
         reference: referenceFrom?.reference)
-      ..fileOffset = charOffset;
+      ..fileOffset = charOffset
+      ..isNonNullableByDefault = true;
   }
 
   Statement _createSetterBody(
diff --git a/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart b/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
index c1191f5183f..4670d129051 100644
--- a/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
@@ -109,11 +109,12 @@ class ProcedureBuilderImpl extends FunctionBuilderImpl
       this._tearOffReferenceFrom,
       [String nativeMethodName])
       : _procedure = new Procedure(null, kind, null,
-            fileUri: compilationUnit?.fileUri,
+            fileUri: compilationUnit.fileUri,
             reference: referenceFrom?.reference)
           ..startFileOffset = startCharOffset
           ..fileOffset = charOffset
-          ..fileEndOffset = charEndOffset,
+          ..fileEndOffset = charEndOffset
+          ..isNonNullableByDefault = compilationUnit.isNonNullableByDefault,
         super(metadata, modifiers, returnType, name, typeVariables, formals,
             compilationUnit, charOffset, nativeMethodName);
 
@@ -453,7 +454,8 @@ class ProcedureBuilderImpl extends FunctionBuilderImpl
       _extensionTearOff ??= new Procedure(null, ProcedureKind.Method, null,
           isStatic: true,
           isExtensionMember: true,
-          reference: _tearOffReferenceFrom?.reference);
+          reference: _tearOffReferenceFrom?.reference)
+        ..isNonNullableByDefault = library.isNonNullableByDefault;
     }
     return _extensionTearOff;
   }
diff --git a/pkg/front_end/lib/src/fasta/dill/dill_class_builder.dart b/pkg/front_end/lib/src/fasta/dill/dill_class_builder.dart
index 2afe2b30bf3..a51997c84cc 100644
--- a/pkg/front_end/lib/src/fasta/dill/dill_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/dill/dill_class_builder.dart
@@ -115,6 +115,9 @@ class DillClassBuilder extends ClassBuilderImpl {
   /// superclass.
   bool get isMixinApplication => cls.isMixinApplication;
 
+  @override
+  bool get hasConstConstructor => cls.hasConstConstructor;
+
   TypeBuilder get mixedInType {
     return computeTypeBuilder(library, cls.mixedInType);
   }
diff --git a/pkg/front_end/lib/src/fasta/incremental_compiler.dart b/pkg/front_end/lib/src/fasta/incremental_compiler.dart
index b58f3415a5a..3711466e5c6 100644
--- a/pkg/front_end/lib/src/fasta/incremental_compiler.dart
+++ b/pkg/front_end/lib/src/fasta/incremental_compiler.dart
@@ -1582,7 +1582,8 @@ class IncrementalCompiler implements IncrementalKernelGenerator {
 
       Procedure procedure = new Procedure(
           new Name(syntheticProcedureName), ProcedureKind.Method, parameters,
-          isStatic: isStatic);
+          isStatic: isStatic)
+        ..isNonNullableByDefault = debugLibrary.isNonNullableByDefault;
 
       parameters.body = new ReturnStatement(compiledExpression)
         ..parent = parameters;
diff --git a/pkg/front_end/lib/src/fasta/kernel/forwarding_node.dart b/pkg/front_end/lib/src/fasta/kernel/forwarding_node.dart
index 6b03c5b9267..f1c505bfb9c 100644
--- a/pkg/front_end/lib/src/fasta/kernel/forwarding_node.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/forwarding_node.dart
@@ -456,7 +456,9 @@ class ForwardingNode {
         reference: referenceFrom?.reference)
       ..startFileOffset = enclosingClass.fileOffset
       ..fileOffset = enclosingClass.fileOffset
-      ..parent = enclosingClass;
+      ..parent = enclosingClass
+      ..isNonNullableByDefault =
+          enclosingClass.enclosingLibrary.isNonNullableByDefault;
   }
 
   /// Returns the [i]th element of [_candidates], finalizing it if necessary.
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index abf58add353..ab9309628c2 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -612,7 +612,8 @@ class KernelTarget extends TargetImplementation {
         initializers: <Initializer>[initializer],
         isSynthetic: true,
         isConst: constructor.isConst && mixin.fields.isEmpty,
-        reference: referenceFrom?.reference);
+        reference: referenceFrom?.reference)
+      ..isNonNullableByDefault = cls.enclosingLibrary.isNonNullableByDefault;
   }
 
   void finishClonedParameters() {
@@ -643,7 +644,9 @@ class KernelTarget extends TargetImplementation {
             returnType: makeConstructorReturnType(enclosingClass)),
         name: new Name(""),
         isSynthetic: true,
-        reference: referenceFrom?.reference);
+        reference: referenceFrom?.reference)
+      ..isNonNullableByDefault =
+          enclosingClass.enclosingLibrary.isNonNullableByDefault;
   }
 
   DartType makeConstructorReturnType(Class enclosingClass) {
diff --git a/pkg/front_end/lib/src/fasta/kernel/load_library_builder.dart b/pkg/front_end/lib/src/fasta/kernel/load_library_builder.dart
index a7669160ebf..4196292e982 100644
--- a/pkg/front_end/lib/src/fasta/kernel/load_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/load_library_builder.dart
@@ -62,7 +62,8 @@ class LoadLibraryBuilder extends BuilderImpl {
         isStatic: true,
         reference: referencesFrom?.reference)
       ..startFileOffset = charOffset
-      ..fileOffset = charOffset;
+      ..fileOffset = charOffset
+      ..isNonNullableByDefault = parent.isNonNullableByDefault;
     return tearoff;
   }
 
diff --git a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
index ea4acbe875f..575cd9b1bd2 100644
--- a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
@@ -170,7 +170,9 @@ class SourceClassBuilder extends ClassBuilderImpl
         referencesFrom = referencesFrom,
         referencesFromIndexed = referencesFromIndexed,
         super(metadata, modifiers, name, typeVariables, supertype, interfaces,
-            onTypes, scope, constructors, parent, nameOffset);
+            onTypes, scope, constructors, parent, nameOffset) {
+    actualCls.hasConstConstructor = hasConstConstructor;
+  }
 
   @override
   Class get cls => origin.actualCls;
@@ -450,7 +452,8 @@ class SourceClassBuilder extends ClassBuilderImpl
             returnType: substitution.substituteType(field.type)),
         fileUri: field.fileUri,
         reference: referenceFrom?.reference)
-      ..fileOffset = field.fileOffset;
+      ..fileOffset = field.fileOffset
+      ..isNonNullableByDefault = cls.enclosingLibrary.isNonNullableByDefault;
     transformProcedureToNoSuchMethodForwarder(noSuchMethod, target, getter);
     cls.procedures.add(getter);
     getter.parent = cls;
@@ -482,7 +485,8 @@ class SourceClassBuilder extends ClassBuilderImpl
             returnType: const VoidType()),
         fileUri: field.fileUri,
         reference: referenceFrom?.reference)
-      ..fileOffset = field.fileOffset;
+      ..fileOffset = field.fileOffset
+      ..isNonNullableByDefault = cls.enclosingLibrary.isNonNullableByDefault;
     transformProcedureToNoSuchMethodForwarder(noSuchMethod, target, setter);
     cls.procedures.add(setter);
     setter.parent = cls;
diff --git a/pkg/front_end/testcases/expression/class_type_param_circular_reference.expression.yaml.expect b/pkg/front_end/testcases/expression/class_type_param_circular_reference.expression.yaml.expect
index e380b764550..d107580800e 100644
--- a/pkg/front_end/testcases/expression/class_type_param_circular_reference.expression.yaml.expect
+++ b/pkg/front_end/testcases/expression/class_type_param_circular_reference.expression.yaml.expect
@@ -1,4 +1,4 @@
 Errors: {
 }
 method /* from org-dartlang-debug:synthetic_debug_expression */ debugExpr() → dynamic
-  return this.{dart.core::Object::toString}();
\ No newline at end of file
+  return this.{dart.core::Object::toString}();
diff --git a/pkg/front_end/testcases/extensions/operators.dart.outline.expect b/pkg/front_end/testcases/extensions/operators.dart.outline.expect
index ca95978e042..2d2d9be0a6f 100644
--- a/pkg/front_end/testcases/extensions/operators.dart.outline.expect
+++ b/pkg/front_end/testcases/extensions/operators.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Complex extends core::Object {
+class Complex extends core::Object /*hasConstConstructor*/  {
   final field core::double* real;
   final field core::double* imaginary;
   const constructor •(core::double* real, core::double* imaginary) → self::Complex*
diff --git a/pkg/front_end/testcases/extensions/operators.dart.strong.expect b/pkg/front_end/testcases/extensions/operators.dart.strong.expect
index 4a46ae4fd01..03710509ad7 100644
--- a/pkg/front_end/testcases/extensions/operators.dart.strong.expect
+++ b/pkg/front_end/testcases/extensions/operators.dart.strong.expect
@@ -13,7 +13,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Complex extends core::Object {
+class Complex extends core::Object /*hasConstConstructor*/  {
   final field core::double* real;
   final field core::double* imaginary;
   const constructor •(core::double* real, core::double* imaginary) → self::Complex*
diff --git a/pkg/front_end/testcases/extensions/operators.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/operators.dart.strong.transformed.expect
index 4a46ae4fd01..03710509ad7 100644
--- a/pkg/front_end/testcases/extensions/operators.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/extensions/operators.dart.strong.transformed.expect
@@ -13,7 +13,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Complex extends core::Object {
+class Complex extends core::Object /*hasConstConstructor*/  {
   final field core::double* real;
   final field core::double* imaginary;
   const constructor •(core::double* real, core::double* imaginary) → self::Complex*
diff --git a/pkg/front_end/testcases/general/DeltaBlue.dart.outline.expect b/pkg/front_end/testcases/general/DeltaBlue.dart.outline.expect
index 0d1797b0843..5d802a54288 100644
--- a/pkg/front_end/testcases/general/DeltaBlue.dart.outline.expect
+++ b/pkg/front_end/testcases/general/DeltaBlue.dart.outline.expect
@@ -8,7 +8,7 @@ class DeltaBlue extends core::Object {
   method run() → void
     ;
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -25,7 +25,7 @@ class Strength extends core::Object {
   static method strongest(self::Strength* s1, self::Strength* s2) → self::Strength*
     ;
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/DeltaBlue.dart.strong.expect b/pkg/front_end/testcases/general/DeltaBlue.dart.strong.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general/DeltaBlue.dart.strong.expect
+++ b/pkg/front_end/testcases/general/DeltaBlue.dart.strong.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/DeltaBlue.dart.strong.transformed.expect b/pkg/front_end/testcases/general/DeltaBlue.dart.strong.transformed.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general/DeltaBlue.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/DeltaBlue.dart.strong.transformed.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.outline.expect b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.outline.expect
index 4c54d2f6ff6..3a9691adf0c 100644
--- a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.outline.expect
+++ b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.outline.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = const <self::Foo*>[self::Foo::bar, self::Foo::baz, self::Foo::cafebabe];
diff --git a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.expect b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.expect
+++ b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.transformed.expect b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.transformed.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/annotation_on_enum_values.dart.strong.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general/annotation_top.dart.outline.expect b/pkg/front_end/testcases/general/annotation_top.dart.outline.expect
index 5fc0262855e..62a6a88c01f 100644
--- a/pkg/front_end/testcases/general/annotation_top.dart.outline.expect
+++ b/pkg/front_end/testcases/general/annotation_top.dart.outline.expect
@@ -6,7 +6,7 @@ import "dart:core" as core;
 
 typedef F1 = () →* void;
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/annotation_top.dart.strong.expect b/pkg/front_end/testcases/general/annotation_top.dart.strong.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general/annotation_top.dart.strong.expect
+++ b/pkg/front_end/testcases/general/annotation_top.dart.strong.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/annotation_top.dart.strong.transformed.expect b/pkg/front_end/testcases/general/annotation_top.dart.strong.transformed.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general/annotation_top.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/annotation_top.dart.strong.transformed.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.outline.expect b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.outline.expect
index 368f1dd9af0..86cd7acdc72 100644
--- a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.outline.expect
+++ b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({named: dynamic}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.expect b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.expect
+++ b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.transformed.expect b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.transformed.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/annotation_variable_declaration.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.outline.expect b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.outline.expect
index 50f5128c6b2..abc752fb226 100644
--- a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.outline.expect
+++ b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.outline.expect
@@ -174,7 +174,7 @@ class Ei<T extends core::Object* = dynamic> = core::Object with self::Empty {
   synthetic constructor •() → self::Ei<self::Ei::T*>*
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -183,7 +183,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
   synthetic constructor •() → self::F<self::F::T*>*
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
   synthetic constructor •() → self::Fc<self::Fc::T*>*
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -201,7 +201,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
   synthetic constructor •() → self::Fi<self::Fi::T*>*
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     ;
 }
@@ -209,7 +209,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
   synthetic constructor •() → self::G<self::G::T*>*
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     ;
 }
@@ -217,7 +217,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
   synthetic constructor •() → self::Gc<self::Gc::T*>*
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     ;
 }
diff --git a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.expect b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.expect
index 74cbe0c1e8c..c4ffb93cc8b 100644
--- a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.expect
+++ b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.expect
@@ -185,7 +185,7 @@ class Ei<T extends core::Object* = dynamic> = core::Object with self::Empty {
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
index 84a65153073..3dae0c6e3ec 100644
--- a/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
@@ -170,22 +170,22 @@ class Di<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::E<self::E::T*>*
     : super core::Object::•()
     ;
 }
-class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ec<self::Ec::T*>*
     : super core::Object::•()
     ;
 }
-class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ei<self::Ei::T*>*
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug33099.dart.outline.expect b/pkg/front_end/testcases/general/bug33099.dart.outline.expect
index 511a3f479b7..8274b912cc2 100644
--- a/pkg/front_end/testcases/general/bug33099.dart.outline.expect
+++ b/pkg/front_end/testcases/general/bug33099.dart.outline.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   method foo() → void
     ;
 }
-abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
+abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug33099.dart.strong.expect b/pkg/front_end/testcases/general/bug33099.dart.strong.expect
index 98cc4a6a675..7bed64471a9 100644
--- a/pkg/front_end/testcases/general/bug33099.dart.strong.expect
+++ b/pkg/front_end/testcases/general/bug33099.dart.strong.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
+abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug33099.dart.strong.transformed.expect b/pkg/front_end/testcases/general/bug33099.dart.strong.transformed.expect
index f56cb2a4371..6cd473f3ab0 100644
--- a/pkg/front_end/testcases/general/bug33099.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/bug33099.dart.strong.transformed.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest {
+abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug34511.dart.outline.expect b/pkg/front_end/testcases/general/bug34511.dart.outline.expect
index cf7dcd39acb..494ce669ad1 100644
--- a/pkg/front_end/testcases/general/bug34511.dart.outline.expect
+++ b/pkg/front_end/testcases/general/bug34511.dart.outline.expect
@@ -6,7 +6,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
   synthetic constructor •() → self::A<self::A::X*>*
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug34511.dart.strong.expect b/pkg/front_end/testcases/general/bug34511.dart.strong.expect
index f743320677e..4de7d7edd42 100644
--- a/pkg/front_end/testcases/general/bug34511.dart.strong.expect
+++ b/pkg/front_end/testcases/general/bug34511.dart.strong.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/bug34511.dart.strong.transformed.expect b/pkg/front_end/testcases/general/bug34511.dart.strong.transformed.expect
index 534c2d32ae5..ffac059549c 100644
--- a/pkg/front_end/testcases/general/bug34511.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/bug34511.dart.strong.transformed.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/clone_function_type.dart.outline.expect b/pkg/front_end/testcases/general/clone_function_type.dart.outline.expect
index 24bf6bcbed8..7ee9fd9f37d 100644
--- a/pkg/front_end/testcases/general/clone_function_type.dart.outline.expect
+++ b/pkg/front_end/testcases/general/clone_function_type.dart.outline.expect
@@ -111,7 +111,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
   synthetic constructor •() → self::Am1<self::Am1::X*, self::Am1::Y*>*
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -120,7 +120,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
   synthetic constructor •() → self::Bm1<self::Bm1::Z*>*
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -129,7 +129,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
   synthetic constructor •() → self::Cm1<self::Cm1::Z*>*
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -138,7 +138,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
   synthetic constructor •() → self::Dm1<self::Dm1::Z*>*
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -147,7 +147,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
   synthetic constructor •() → self::Em1<self::Em1::Z*>*
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -156,7 +156,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
   synthetic constructor •() → self::Fm1<self::Fm1::Z*>*
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -165,7 +165,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
   synthetic constructor •() → self::Gm1<self::Gm1::Z*>*
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -174,7 +174,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
   synthetic constructor •() → self::Hm1<self::Hm1::Z*>*
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -183,7 +183,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
   synthetic constructor •() → self::Im1<self::Im1::Z*>*
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
   synthetic constructor •() → self::Jm1<self::Jm1::Z*>*
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -201,7 +201,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
   synthetic constructor •() → self::Km1<self::Km1::Z*>*
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -269,7 +269,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
   synthetic constructor •() → self::Am2<self::Am2::X*, self::Am2::Y*>*
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -278,7 +278,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
   synthetic constructor •() → self::Bm2<self::Bm2::Z*>*
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -287,7 +287,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
   synthetic constructor •() → self::Cm2<self::Cm2::Z*>*
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -296,7 +296,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
   synthetic constructor •() → self::Dm2<self::Dm2::Z*>*
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -305,7 +305,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
   synthetic constructor •() → self::Em2<self::Em2::Z*>*
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -314,7 +314,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
   synthetic constructor •() → self::Fm2<self::Fm2::Z*>*
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -323,7 +323,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
   synthetic constructor •() → self::Gm2<self::Gm2::Z*>*
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
   synthetic constructor •() → self::Hm2<self::Hm2::Z*>*
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -341,7 +341,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
   synthetic constructor •() → self::Im2<self::Im2::Z*>*
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -350,7 +350,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
   synthetic constructor •() → self::Jm2<self::Jm2::Z*>*
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -359,7 +359,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
   synthetic constructor •() → self::Km2<self::Km2::Z*>*
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -427,7 +427,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
   synthetic constructor •() → self::Am3<self::Am3::L*, self::Am3::Y*>*
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -436,7 +436,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
   synthetic constructor •() → self::Bm3<self::Bm3::Z*>*
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -445,7 +445,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
   synthetic constructor •() → self::Cm3<self::Cm3::Z*>*
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -454,7 +454,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
   synthetic constructor •() → self::Dm3<self::Dm3::Z*>*
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -463,7 +463,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
   synthetic constructor •() → self::Em3<self::Em3::Z*>*
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
   synthetic constructor •() → self::Fm3<self::Fm3::Z*>*
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -481,7 +481,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
   synthetic constructor •() → self::Gm3<self::Gm3::Z*>*
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -490,7 +490,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
   synthetic constructor •() → self::Hm3<self::Hm3::Z*>*
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -499,7 +499,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
   synthetic constructor •() → self::Im3<self::Im3::Z*>*
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -508,7 +508,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
   synthetic constructor •() → self::Jm3<self::Jm3::Z*>*
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/clone_function_type.dart.strong.expect b/pkg/front_end/testcases/general/clone_function_type.dart.strong.expect
index e2c3c3cc5c5..c287cae9820 100644
--- a/pkg/front_end/testcases/general/clone_function_type.dart.strong.expect
+++ b/pkg/front_end/testcases/general/clone_function_type.dart.strong.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/clone_function_type.dart.strong.transformed.expect b/pkg/front_end/testcases/general/clone_function_type.dart.strong.transformed.expect
index 4c9590f6946..071ec095807 100644
--- a/pkg/front_end/testcases/general/clone_function_type.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/clone_function_type.dart.strong.transformed.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -222,57 +222,57 @@ class Lm1<Z extends core::Object* = dynamic> extends self::_Lm1&Object&Am1<self:
     : super self::_Lm1&Object&Am1::•()
     ;
 }
-class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> {
+class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm1<self::Mm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> {
+class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm1<self::Nm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> {
+class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om1<self::Om1::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> {
+class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm1<self::Pm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> {
+class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm1<self::Qm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> {
+class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm1<self::Rm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> {
+class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm1<self::Sm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> {
+class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm1<self::Tm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> {
+class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um1<self::Um1::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> {
+class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm1<self::Vm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> {
+class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm1<self::Wm1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -392,57 +392,57 @@ class Lm2<Z extends core::Object* = dynamic> extends self::_Lm2&Object&Am2<self:
     : super self::_Lm2&Object&Am2::•()
     ;
 }
-class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> {
+class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm2<self::Mm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> {
+class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm2<self::Nm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> {
+class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om2<self::Om2::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> {
+class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm2<self::Pm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> {
+class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm2<self::Qm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> {
+class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm2<self::Rm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> {
+class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm2<self::Sm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> {
+class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm2<self::Tm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> {
+class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um2<self::Um2::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> {
+class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm2<self::Vm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> {
+class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm2<self::Wm2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.outline.expect b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.outline.expect
index fbca3b488b1..a68c8ab2229 100644
--- a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.outline.expect
+++ b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.outline.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.expect b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.expect
index 29828dbe124..1b410011eb1 100644
--- a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.expect
+++ b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.transformed.expect b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
index 29828dbe124..1b410011eb1 100644
--- a/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.outline.expect b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.outline.expect
index fdcd4b7a5bd..d28ec62488f 100644
--- a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.outline.expect
+++ b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.outline.expect
@@ -9,14 +9,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.expect b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.expect
index 3022157668e..12ac4326cca 100644
--- a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.expect
+++ b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.transformed.expect b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.transformed.expect
index 3022157668e..12ac4326cca 100644
--- a/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/const_redirect_to_nonconst.dart.strong.transformed.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general/constructor_const_inference.dart.outline.expect b/pkg/front_end/testcases/general/constructor_const_inference.dart.outline.expect
index 6cda74d5595..934d099c09c 100644
--- a/pkg/front_end/testcases/general/constructor_const_inference.dart.outline.expect
+++ b/pkg/front_end/testcases/general/constructor_const_inference.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.expect b/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.expect
+++ b/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.transformed.expect b/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.transformed.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/constructor_const_inference.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
index d8dce848e5c..f2001a3c182 100644
--- a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
+++ b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
   method foo(core::num* x) → void
     ;
 }
-abstract class _D&A&B = self::A with self::B {
+abstract class _D&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
index 08d745d6180..03d861d3c7a 100644
--- a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
+++ b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B = self::A with self::B {
+abstract class _D&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
index 24f8755123a..b35ef09c679 100644
--- a/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B extends self::A implements self::B {
+abstract class _D&A&B extends self::A implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general/duplicated_declarations.dart.outline.expect b/pkg/front_end/testcases/general/duplicated_declarations.dart.outline.expect
index b190f3a70ca..70afe008b90 100644
--- a/pkg/front_end/testcases/general/duplicated_declarations.dart.outline.expect
+++ b/pkg/front_end/testcases/general/duplicated_declarations.dart.outline.expect
@@ -359,7 +359,7 @@ class Sub extends core::Object {
   method m() → dynamic
     ;
 }
-class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#4 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#4*>* values = const <self::Enum#4*>[self::Enum#4::a];
@@ -370,7 +370,7 @@ class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#4::_name};
 }
-class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#3 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#3*>* values = const <self::Enum#3*>[self::Enum#3::a, self::Enum#3::b, self::Enum#3::c];
@@ -383,7 +383,7 @@ class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#3::_name};
 }
-class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#2 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#2*>* values = const <self::Enum#2*>[self::Enum#2::Enum, self::Enum#2::a, self::Enum#2::b];
@@ -396,7 +396,7 @@ class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#2::_name};
 }
-class Enum#1 extends core::Object {
+class Enum#1 extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#1*>* values = const <self::Enum#1*>[self::Enum#1::a, self::Enum#1::b, self::Enum#1::c];
@@ -409,7 +409,7 @@ class Enum#1 extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum#1::_name};
 }
-class Enum extends core::Object {
+class Enum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum*>* values = const <self::Enum*>[self::Enum::Enum, self::Enum::a, self::Enum::b];
@@ -422,7 +422,7 @@ class Enum extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum::_name};
 }
-class AnotherEnum extends core::Object {
+class AnotherEnum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::AnotherEnum*>* values = const <self::AnotherEnum*>[self::AnotherEnum::a, self::AnotherEnum::b, self::AnotherEnum::c];
diff --git a/pkg/front_end/testcases/general/duplicated_declarations.dart.strong.expect b/pkg/front_end/testcases/general/duplicated_declarations.dart.strong.expect
index 71677b28e6c..888b9d865a6 100644
--- a/pkg/front_end/testcases/general/duplicated_declarations.dart.strong.expect
+++ b/pkg/front_end/testcases/general/duplicated_declarations.dart.strong.expect
@@ -421,7 +421,7 @@ Try removing the extra positional arguments.
   method m() → dynamic
     return super.m();
 }
-class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#4 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#4*>* values = #C4;
@@ -432,7 +432,7 @@ class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#4::_name};
 }
-class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#3 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#3*>* values = #C12;
@@ -445,7 +445,7 @@ class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#3::_name};
 }
-class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#2 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#2*>* values = #C17;
@@ -458,7 +458,7 @@ class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#2::_name};
 }
-class Enum#1 extends core::Object {
+class Enum#1 extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#1*>* values = #C21;
@@ -471,7 +471,7 @@ class Enum#1 extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum#1::_name};
 }
-class Enum extends core::Object {
+class Enum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum*>* values = #C25;
@@ -484,7 +484,7 @@ class Enum extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum::_name};
 }
-class AnotherEnum extends core::Object {
+class AnotherEnum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::AnotherEnum*>* values = #C32;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.outline.expect b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.outline.expect
index 14fe62f7bbe..1e369aeb5c4 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.outline.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.outline.expect
@@ -11,7 +11,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.expect b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.expect
index 3df9b64d181..082c2d44214 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.transformed.expect b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.transformed.expect
index 3df9b64d181..082c2d44214 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_01.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.outline.expect b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.outline.expect
index 25620a04c20..15ae178db74 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.outline.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.outline.expect
@@ -12,7 +12,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.expect b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.expect
index efddc108164..f617628e399 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.transformed.expect b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.transformed.expect
index efddc108164..f617628e399 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_02.dart.strong.transformed.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.outline.expect b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.outline.expect
index e2689c9be02..8e00ee1e1d0 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.outline.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.outline.expect
@@ -12,7 +12,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.expect b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.expect
index 4028b042256..a9264537189 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.transformed.expect b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.transformed.expect
index 4028b042256..a9264537189 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_03.dart.strong.transformed.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.outline.expect b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.outline.expect
index 4034b8b04d7..8406a72d0a7 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.outline.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.outline.expect
@@ -11,7 +11,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -26,7 +26,7 @@ import "error_location_04_lib1.dart" as self2;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field self2::Foo* x;
   const constructor •() → self3::Bar*
     : self3::Bar::x = const self2::Foo::•(0), super core::Object::•()
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.expect b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.expect
index ac754c7b02b..0b9da71176b 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.transformed.expect b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.transformed.expect
index ac754c7b02b..0b9da71176b 100644
--- a/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/error_locations/error_location_04.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general/extend_with_type_variable.dart.outline.expect b/pkg/front_end/testcases/general/extend_with_type_variable.dart.outline.expect
index c76d70144ae..ac516b1ae2a 100644
--- a/pkg/front_end/testcases/general/extend_with_type_variable.dart.outline.expect
+++ b/pkg/front_end/testcases/general/extend_with_type_variable.dart.outline.expect
@@ -21,9 +21,9 @@ class SuperClass extends core::Object {
   synthetic constructor •() → self::SuperClass*
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     ;
 }
@@ -31,7 +31,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
   synthetic constructor •() → self::Class1<self::Class1::T*, self::Class1::S*>*
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.expect b/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.expect
index bc9f1ea34cc..fc89e52b0ce 100644
--- a/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.expect
+++ b/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.transformed.expect b/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.transformed.expect
index e38b62f7973..c3f0a091b51 100644
--- a/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/extend_with_type_variable.dart.strong.transformed.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.outline.expect b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.outline.expect
index 55f17dd45a5..503d2efd079 100644
--- a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.outline.expect
+++ b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = 87;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.expect b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.expect
+++ b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.transformed.expect b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.transformed.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/implicit_const_with_static_fields.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general/issue37776.dart.outline.expect b/pkg/front_end/testcases/general/issue37776.dart.outline.expect
index bb2fbfaafe6..a055aeb7266 100644
--- a/pkg/front_end/testcases/general/issue37776.dart.outline.expect
+++ b/pkg/front_end/testcases/general/issue37776.dart.outline.expect
@@ -12,12 +12,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue37776.dart.strong.expect b/pkg/front_end/testcases/general/issue37776.dart.strong.expect
index 481a71dd57a..f0888c6d480 100644
--- a/pkg/front_end/testcases/general/issue37776.dart.strong.expect
+++ b/pkg/front_end/testcases/general/issue37776.dart.strong.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue37776.dart.strong.transformed.expect b/pkg/front_end/testcases/general/issue37776.dart.strong.transformed.expect
index 481a71dd57a..f0888c6d480 100644
--- a/pkg/front_end/testcases/general/issue37776.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/issue37776.dart.strong.transformed.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue38944.dart.outline.expect b/pkg/front_end/testcases/general/issue38944.dart.outline.expect
index a4f21685afc..4c9456cf539 100644
--- a/pkg/front_end/testcases/general/issue38944.dart.outline.expect
+++ b/pkg/front_end/testcases/general/issue38944.dart.outline.expect
@@ -13,7 +13,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
   synthetic constructor •() → self::A<self::A::Q*>*
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue38944.dart.strong.expect b/pkg/front_end/testcases/general/issue38944.dart.strong.expect
index 06fa5034269..d6a3d0aadf9 100644
--- a/pkg/front_end/testcases/general/issue38944.dart.strong.expect
+++ b/pkg/front_end/testcases/general/issue38944.dart.strong.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue38944.dart.strong.transformed.expect b/pkg/front_end/testcases/general/issue38944.dart.strong.transformed.expect
index 06fa5034269..d6a3d0aadf9 100644
--- a/pkg/front_end/testcases/general/issue38944.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/issue38944.dart.strong.transformed.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/issue40428.dart.strong.transformed.expect b/pkg/front_end/testcases/general/issue40428.dart.strong.transformed.expect
index 11cf47600f2..bbfe989362c 100644
--- a/pkg/front_end/testcases/general/issue40428.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/issue40428.dart.strong.transformed.expect
@@ -30,12 +30,12 @@ class Mixin extends core::Object {
     : super core::Object::•()
     ;
 }
-class NamedMixin1 extends self::SuperClass1 implements self::Mixin {
+class NamedMixin1 extends self::SuperClass1 implements self::Mixin /*isEliminatedMixin*/  {
   synthetic constructor •(core::String* value) → self::NamedMixin1*
     : super self::SuperClass1::•(value)
     ;
 }
-class NamedMixin2 extends self::SuperClass2 implements self::Mixin {
+class NamedMixin2 extends self::SuperClass2 implements self::Mixin /*isEliminatedMixin*/  {
   synthetic constructor •(core::String* i) → self::NamedMixin2*
     : super self::SuperClass2::•(i)
     ;
diff --git a/pkg/front_end/testcases/general/magic_const.dart.outline.expect b/pkg/front_end/testcases/general/magic_const.dart.outline.expect
index 02428e5063f..9eab40cfac7 100644
--- a/pkg/front_end/testcases/general/magic_const.dart.outline.expect
+++ b/pkg/front_end/testcases/general/magic_const.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/magic_const.dart.strong.expect b/pkg/front_end/testcases/general/magic_const.dart.strong.expect
index 7f979c690ab..d37f679eb3c 100644
--- a/pkg/front_end/testcases/general/magic_const.dart.strong.expect
+++ b/pkg/front_end/testcases/general/magic_const.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/magic_const.dart.strong.transformed.expect b/pkg/front_end/testcases/general/magic_const.dart.strong.transformed.expect
index 7f979c690ab..d37f679eb3c 100644
--- a/pkg/front_end/testcases/general/magic_const.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/magic_const.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/many_errors.dart.outline.expect b/pkg/front_end/testcases/general/many_errors.dart.outline.expect
index 84857107525..09f5a30dfaf 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.outline.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.outline.expect
@@ -30,7 +30,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     ;
@@ -50,7 +50,7 @@ class C extends core::Object {
   synthetic constructor •() → self::C*
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/many_errors.dart.strong.expect b/pkg/front_end/testcases/general/many_errors.dart.strong.expect
index 0f7aef3a98d..7dd3401272a 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.strong.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.strong.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general/many_errors.dart:8:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect b/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
index 0f7aef3a98d..7dd3401272a 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general/many_errors.dart:8:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/metadata_enum.dart.outline.expect b/pkg/front_end/testcases/general/metadata_enum.dart.outline.expect
index 7c3363ef06e..8944460c5b5 100644
--- a/pkg/front_end/testcases/general/metadata_enum.dart.outline.expect
+++ b/pkg/front_end/testcases/general/metadata_enum.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @self::a
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = const <self::E*>[self::E::E1, self::E::E2, self::E::E3];
diff --git a/pkg/front_end/testcases/general/metadata_enum.dart.strong.expect b/pkg/front_end/testcases/general/metadata_enum.dart.strong.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general/metadata_enum.dart.strong.expect
+++ b/pkg/front_end/testcases/general/metadata_enum.dart.strong.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general/metadata_enum.dart.strong.transformed.expect b/pkg/front_end/testcases/general/metadata_enum.dart.strong.transformed.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general/metadata_enum.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/metadata_enum.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general/metadata_named_mixin_application.dart.strong.transformed.expect b/pkg/front_end/testcases/general/metadata_named_mixin_application.dart.strong.transformed.expect
index 5cd563596cf..1b24fb63151 100644
--- a/pkg/front_end/testcases/general/metadata_named_mixin_application.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/metadata_named_mixin_application.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class C extends self::D implements self::E {
+class C extends self::D implements self::E /*isEliminatedMixin*/  {
   synthetic constructor •() → self::C*
     : super self::D::•()
     ;
diff --git a/pkg/front_end/testcases/general/missing_constructor.dart.outline.expect b/pkg/front_end/testcases/general/missing_constructor.dart.outline.expect
index 4436b0df6bb..a50e142a940 100644
--- a/pkg/front_end/testcases/general/missing_constructor.dart.outline.expect
+++ b/pkg/front_end/testcases/general/missing_constructor.dart.outline.expect
@@ -22,7 +22,7 @@ class M extends core::Object {
   synthetic constructor •() → self::M*
     ;
 }
-abstract class _MixinApplication&Super&M = self::Super with self::M {
+abstract class _MixinApplication&Super&M = self::Super with self::M /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general/missing_constructor.dart.strong.expect b/pkg/front_end/testcases/general/missing_constructor.dart.strong.expect
index 7d2527a3624..1cadfeadd32 100644
--- a/pkg/front_end/testcases/general/missing_constructor.dart.strong.expect
+++ b/pkg/front_end/testcases/general/missing_constructor.dart.strong.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M = self::Super with self::M {
+abstract class _MixinApplication&Super&M = self::Super with self::M /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general/missing_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/general/missing_constructor.dart.strong.transformed.expect
index 756b1cf865c..b77e9a04c33 100644
--- a/pkg/front_end/testcases/general/missing_constructor.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/missing_constructor.dart.strong.transformed.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M extends self::Super implements self::M {
+abstract class _MixinApplication&Super&M extends self::Super implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general/mixin.dart.outline.expect b/pkg/front_end/testcases/general/mixin.dart.outline.expect
index a53c688a3f4..9a57e2960b1 100644
--- a/pkg/front_end/testcases/general/mixin.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin.dart.outline.expect
@@ -2,12 +2,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 = core::Object with self::M1 {
+abstract class _B&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 {
+abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -28,12 +28,12 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     ;
 }
-abstract class _C&Object&M1 = core::Object with self::M1 {
+abstract class _C&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 {
+abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -48,7 +48,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     ;
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin.dart.strong.expect b/pkg/front_end/testcases/general/mixin.dart.strong.expect
index 4873d85b11c..2cca9cf0caf 100644
--- a/pkg/front_end/testcases/general/mixin.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin.dart.strong.expect
@@ -2,12 +2,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 = core::Object with self::M1 {
+abstract class _B&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 {
+abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -31,12 +31,12 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 = core::Object with self::M1 {
+abstract class _C&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 {
+abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -53,7 +53,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin.dart.strong.transformed.expect
index b36e425650d..b51ef02e7d2 100644
--- a/pkg/front_end/testcases/general/mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin.dart.strong.transformed.expect
@@ -2,14 +2,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 extends core::Object implements self::M1 {
+abstract class _B&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 {
+abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -35,14 +35,14 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 extends core::Object implements self::M1 {
+abstract class _C&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 {
+abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -61,7 +61,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_application_inferred_parameter_type.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
index 44d03d04e79..baf01a71a83 100644
--- a/pkg/front_end/testcases/general/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class Super extends core::Object {
     : self::Super::field = field, super core::Object::•()
     ;
 }
-class Class extends self::Super implements self::Mixin {
+class Class extends self::Super implements self::Mixin /*isEliminatedMixin*/  {
   synthetic constructor •(core::int* field) → self::Class*
     : super self::Super::•(field)
     ;
diff --git a/pkg/front_end/testcases/general/mixin_application_override.dart.outline.expect b/pkg/front_end/testcases/general/mixin_application_override.dart.outline.expect
index 5454a334592..00b6b5b3bf2 100644
--- a/pkg/front_end/testcases/general/mixin_application_override.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_application_override.dart.outline.expect
@@ -155,7 +155,7 @@ class A0 = self::S with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A1&S&M1 = self::S with self::M1 {
+abstract class _A1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1&S&M1*
     : super self::S::•()
     ;
@@ -166,12 +166,12 @@ class A1 = self::_A1&S&M1 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A2&S&M1 = self::S with self::M1 {
+abstract class _A2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 {
+abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1&M2*
     : super self::_A2&S&M1::•()
     ;
@@ -182,7 +182,7 @@ class A2 = self::_A2&S&M1&M2 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A0X&S&M = self::S with self::M {
+abstract class _A0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A0X&S&M*
     : super self::S::•()
     ;
@@ -193,12 +193,12 @@ class A0X = self::_A0X&S&M with self::MX {
     : super self::_A0X&S&M::•()
     ;
 }
-abstract class _A1X&S&M1 = self::S with self::M1 {
+abstract class _A1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M {
+abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1&M*
     : super self::_A1X&S&M1::•()
     ;
@@ -209,17 +209,17 @@ class A1X = self::_A1X&S&M1&M with self::MX {
     : super self::_A1X&S&M1&M::•()
     ;
 }
-abstract class _A2X&S&M1 = self::S with self::M1 {
+abstract class _A2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 {
+abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2*
     : super self::_A2X&S&M1::•()
     ;
 }
-abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M {
+abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2&M*
     : super self::_A2X&S&M1&M2::•()
     ;
@@ -230,7 +230,7 @@ class A2X = self::_A2X&S&M1&M2&M with self::MX {
     : super self::_A2X&S&M1&M2&M::•()
     ;
 }
-abstract class _B0&S&M = self::S with self::M {
+abstract class _B0&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0&S&M*
     : super self::S::•()
     ;
@@ -240,12 +240,12 @@ class B0 extends self::_B0&S&M {
   synthetic constructor •() → self::B0*
     ;
 }
-abstract class _B1&S&M1 = self::S with self::M1 {
+abstract class _B1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M {
+abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1&M*
     : super self::_B1&S&M1::•()
     ;
@@ -255,17 +255,17 @@ class B1 extends self::_B1&S&M1&M {
   synthetic constructor •() → self::B1*
     ;
 }
-abstract class _B2&S&M1 = self::S with self::M1 {
+abstract class _B2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 {
+abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2*
     : super self::_B2&S&M1::•()
     ;
 }
-abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M {
+abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2&M*
     : super self::_B2&S&M1&M2::•()
     ;
@@ -275,13 +275,13 @@ class B2 extends self::_B2&S&M1&M2&M {
   synthetic constructor •() → self::B2*
     ;
 }
-abstract class _B0X&S&M = self::S with self::M {
+abstract class _B0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M*
     : super self::S::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX {
+abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M&MX*
     : super self::_B0X&S&M::•()
     ;
@@ -290,18 +290,18 @@ class B0X extends self::_B0X&S&M&MX {
   synthetic constructor •() → self::B0X*
     ;
 }
-abstract class _B1X&S&M1 = self::S with self::M1 {
+abstract class _B1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M {
+abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M*
     : super self::_B1X&S&M1::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX {
+abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M&MX*
     : super self::_B1X&S&M1&M::•()
     ;
@@ -310,23 +310,23 @@ class B1X extends self::_B1X&S&M1&M&MX {
   synthetic constructor •() → self::B1X*
     ;
 }
-abstract class _B2X&S&M1 = self::S with self::M1 {
+abstract class _B2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 {
+abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2*
     : super self::_B2X&S&M1::•()
     ;
 }
-abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M {
+abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M*
     : super self::_B2X&S&M1&M2::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX {
+abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M&MX*
     : super self::_B2X&S&M1&M2&M::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_application_override.dart.strong.expect b/pkg/front_end/testcases/general/mixin_application_override.dart.strong.expect
index d304cbd13d1..fca000ef317 100644
--- a/pkg/front_end/testcases/general/mixin_application_override.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_application_override.dart.strong.expect
@@ -158,7 +158,7 @@ class A0 = self::S with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A1&S&M1 = self::S with self::M1 {
+abstract class _A1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1&S&M1*
     : super self::S::•()
     ;
@@ -169,12 +169,12 @@ class A1 = self::_A1&S&M1 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A2&S&M1 = self::S with self::M1 {
+abstract class _A2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 {
+abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1&M2*
     : super self::_A2&S&M1::•()
     ;
@@ -185,7 +185,7 @@ class A2 = self::_A2&S&M1&M2 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A0X&S&M = self::S with self::M {
+abstract class _A0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A0X&S&M*
     : super self::S::•()
     ;
@@ -196,12 +196,12 @@ class A0X = self::_A0X&S&M with self::MX {
     : super self::_A0X&S&M::•()
     ;
 }
-abstract class _A1X&S&M1 = self::S with self::M1 {
+abstract class _A1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M {
+abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1&M*
     : super self::_A1X&S&M1::•()
     ;
@@ -212,17 +212,17 @@ class A1X = self::_A1X&S&M1&M with self::MX {
     : super self::_A1X&S&M1&M::•()
     ;
 }
-abstract class _A2X&S&M1 = self::S with self::M1 {
+abstract class _A2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 {
+abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2*
     : super self::_A2X&S&M1::•()
     ;
 }
-abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M {
+abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2&M*
     : super self::_A2X&S&M1&M2::•()
     ;
@@ -233,7 +233,7 @@ class A2X = self::_A2X&S&M1&M2&M with self::MX {
     : super self::_A2X&S&M1&M2&M::•()
     ;
 }
-abstract class _B0&S&M = self::S with self::M {
+abstract class _B0&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0&S&M*
     : super self::S::•()
     ;
@@ -244,12 +244,12 @@ class B0 extends self::_B0&S&M {
     : super self::_B0&S&M::•()
     ;
 }
-abstract class _B1&S&M1 = self::S with self::M1 {
+abstract class _B1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M {
+abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1&M*
     : super self::_B1&S&M1::•()
     ;
@@ -260,17 +260,17 @@ class B1 extends self::_B1&S&M1&M {
     : super self::_B1&S&M1&M::•()
     ;
 }
-abstract class _B2&S&M1 = self::S with self::M1 {
+abstract class _B2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 {
+abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2*
     : super self::_B2&S&M1::•()
     ;
 }
-abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M {
+abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2&M*
     : super self::_B2&S&M1&M2::•()
     ;
@@ -281,13 +281,13 @@ class B2 extends self::_B2&S&M1&M2&M {
     : super self::_B2&S&M1&M2&M::•()
     ;
 }
-abstract class _B0X&S&M = self::S with self::M {
+abstract class _B0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M*
     : super self::S::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX {
+abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M&MX*
     : super self::_B0X&S&M::•()
     ;
@@ -297,18 +297,18 @@ class B0X extends self::_B0X&S&M&MX {
     : super self::_B0X&S&M&MX::•()
     ;
 }
-abstract class _B1X&S&M1 = self::S with self::M1 {
+abstract class _B1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M {
+abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M*
     : super self::_B1X&S&M1::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX {
+abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M&MX*
     : super self::_B1X&S&M1&M::•()
     ;
@@ -318,23 +318,23 @@ class B1X extends self::_B1X&S&M1&M&MX {
     : super self::_B1X&S&M1&M&MX::•()
     ;
 }
-abstract class _B2X&S&M1 = self::S with self::M1 {
+abstract class _B2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 {
+abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2*
     : super self::_B2X&S&M1::•()
     ;
 }
-abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M {
+abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M*
     : super self::_B2X&S&M1&M2::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX {
+abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M&MX*
     : super self::_B2X&S&M1&M2&M::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_conflicts.dart.outline.expect b/pkg/front_end/testcases/general/mixin_conflicts.dart.outline.expect
index f5bee664024..87dfa06d0f8 100644
--- a/pkg/front_end/testcases/general/mixin_conflicts.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_conflicts.dart.outline.expect
@@ -44,7 +44,7 @@ class N = core::Object with self::M {
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&N = core::Object with self::N {
+abstract class _C&Object&N = core::Object with self::N /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -69,7 +69,7 @@ abstract class N3 = core::Object with self::M2 {
     : super core::Object::•()
     ;
 }
-abstract class _C2&Object&M2 = core::Object with self::M2 {
+abstract class _C2&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -78,7 +78,7 @@ class C2 extends self::_C2&Object&M2 {
   synthetic constructor •() → self::C2*
     ;
 }
-abstract class _C3&Object&M2 = core::Object with self::M2 {
+abstract class _C3&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.expect b/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.expect
index b4e3d5aa521..73140d2e1f8 100644
--- a/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.expect
@@ -44,7 +44,7 @@ class N = core::Object with self::M {
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&N = core::Object with self::N {
+abstract class _C&Object&N = core::Object with self::N /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -70,7 +70,7 @@ abstract class N3 = core::Object with self::M2 {
     : super core::Object::•()
     ;
 }
-abstract class _C2&Object&M2 = core::Object with self::M2 {
+abstract class _C2&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -80,7 +80,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 = core::Object with self::M2 {
+abstract class _C3&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.transformed.expect
index dcb89f067de..52ec3adf486 100644
--- a/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_conflicts.dart.strong.transformed.expect
@@ -39,13 +39,13 @@ class M extends core::Object {
     ;
   method foo() → dynamic {}
 }
-class N extends core::Object implements self::M {
+class N extends core::Object implements self::M /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N*
     : super core::Object::•()
     ;
   method foo() → dynamic {}
 }
-abstract class _C&Object&N extends core::Object implements self::N {
+abstract class _C&Object&N extends core::Object implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -62,19 +62,19 @@ abstract class M2 extends core::Object implements self::M {
     ;
   method bar() → dynamic {}
 }
-class N2 extends core::Object implements self::M2 {
+class N2 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N2*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class N3 extends core::Object implements self::M2 {
+abstract class N3 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N3*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class _C2&Object&M2 extends core::Object implements self::M2 {
+abstract class _C2&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -85,7 +85,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 extends core::Object implements self::M2 {
+abstract class _C3&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.outline.expect b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.outline.expect
index 7c8f4ee13a1..9c0a4edfa85 100644
--- a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.outline.expect
@@ -22,7 +22,7 @@ class E extends self::D {
   synthetic constructor •() → self::E*
     ;
 }
-abstract class _F&C&M = self::C<core::int*> with self::M {
+abstract class _F&C&M = self::C<core::int*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •({dynamic a, dynamic b}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.expect b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.expect
index 7998fd739f0..153bb13ab58 100644
--- a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.expect
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M = self::C<core::int*> with self::M {
+abstract class _F&C&M = self::C<core::int*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.transformed.expect
index 05cc2ceac9d..b2dbf88c3da 100644
--- a/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_constructors_with_default_values.dart.strong.transformed.expect
@@ -29,7 +29,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class D extends self::C<core::String*> implements self::M {
+class D extends self::C<core::String*> implements self::M /*isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C2}) → self::D*
     : super self::C::•(a: a, b: b)
     ;
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M extends self::C<core::int*> implements self::M {
+abstract class _F&C&M extends self::C<core::int*> implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
index 5d6839715e7..3b41508ff8d 100644
--- a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
@@ -17,7 +17,7 @@ class D extends self::C<self::B*> {
   synthetic constructor •() → self::D*
     ;
 }
-abstract class _Foo&Object&C = core::Object with self::C<self::B*> {
+abstract class _Foo&Object&C = core::Object with self::C<self::B*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
index 9081947fb10..467b3b598ba 100644
--- a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C = core::Object with self::C<self::B*> {
+abstract class _Foo&Object&C = core::Object with self::C<self::B*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
index 8d9258937c7..6b9150f933c 100644
--- a/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> {
+abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> /*isAnonymousMixin,isEliminatedMixin*/  {
   generic-covariant-impl field self::B* _field = null;
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general/mixin_super_repeated.dart.outline.expect b/pkg/front_end/testcases/general/mixin_super_repeated.dart.outline.expect
index 7e6110bd9eb..13e9d2562b8 100644
--- a/pkg/front_end/testcases/general/mixin_super_repeated.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_super_repeated.dart.outline.expect
@@ -19,12 +19,12 @@ class S extends core::Object {
   synthetic constructor •() → self::S*
     ;
 }
-abstract class _Named&S&M = self::S with self::M {
+abstract class _Named&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N = self::_Named&S&M with self::N {
+abstract class _Named&S&M&N = self::_Named&S&M with self::N /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.expect b/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.expect
index 1dc80512eb5..085e258a30e 100644
--- a/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.expect
@@ -23,12 +23,12 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M = self::S with self::M {
+abstract class _Named&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N = self::_Named&S&M with self::N {
+abstract class _Named&S&M&N = self::_Named&S&M with self::N /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.transformed.expect
index 14cb42dd3f8..ad780133565 100644
--- a/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_super_repeated.dart.strong.transformed.expect
@@ -23,13 +23,13 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M extends self::S implements self::M {
+abstract class _Named&S&M extends self::S implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
+abstract class _Named&S&M&N extends self::_Named&S&M implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
@@ -39,7 +39,7 @@ abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
   get superM() → dynamic
     return super.{self::M::m};
 }
-class Named extends self::_Named&S&M&N implements self::M {
+class Named extends self::_Named&S&M&N implements self::M /*isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::Named*
     : super self::_Named&S&M&N::•()
diff --git a/pkg/front_end/testcases/general/mixin_with_static_member.dart.outline.expect b/pkg/front_end/testcases/general/mixin_with_static_member.dart.outline.expect
index c82f01d24e0..f982247c68d 100644
--- a/pkg/front_end/testcases/general/mixin_with_static_member.dart.outline.expect
+++ b/pkg/front_end/testcases/general/mixin_with_static_member.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M = self::B with self::M {
+abstract class _A&B&M = self::B with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.expect b/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.expect
index a6968d34727..85e498d6a9d 100644
--- a/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.expect
+++ b/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M = self::B with self::M {
+abstract class _A&B&M = self::B with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.transformed.expect
index a7328585c77..b9faaa3b7cc 100644
--- a/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/mixin_with_static_member.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M extends self::B implements self::M {
+abstract class _A&B&M extends self::B implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.outline.expect b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.outline.expect
index 536cae19a94..f42f11fb9b4 100644
--- a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.outline.expect
+++ b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.outline.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.expect b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.expect
+++ b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.transformed.expect b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.transformed.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/nested_implicit_const_with_env_var.dart.strong.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general/qualified.dart.outline.expect b/pkg/front_end/testcases/general/qualified.dart.outline.expect
index c8750b50b99..8e9513fda51 100644
--- a/pkg/front_end/testcases/general/qualified.dart.outline.expect
+++ b/pkg/front_end/testcases/general/qualified.dart.outline.expect
@@ -34,7 +34,7 @@ class Bad extends core::Object {
   static factory WrongName() → self::Bad*
     ;
 }
-abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general/qualified.dart.strong.expect b/pkg/front_end/testcases/general/qualified.dart.strong.expect
index 5b18e11a3da..d55988fb561 100644
--- a/pkg/front_end/testcases/general/qualified.dart.strong.expect
+++ b/pkg/front_end/testcases/general/qualified.dart.strong.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general/qualified.dart.strong.transformed.expect b/pkg/front_end/testcases/general/qualified.dart.strong.transformed.expect
index f45751fa714..21eaf086a3a 100644
--- a/pkg/front_end/testcases/general/qualified.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/qualified.dart.strong.transformed.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general/redirecting_factory.dart.strong.transformed.expect b/pkg/front_end/testcases/general/redirecting_factory.dart.strong.transformed.expect
index c9e154bf1f3..f5c4fb61b24 100644
--- a/pkg/front_end/testcases/general/redirecting_factory.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/redirecting_factory.dart.strong.transformed.expect
@@ -62,7 +62,7 @@ class Mixin<M extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> {
+class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Mix<self::Mix::M*>*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.outline.expect b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.outline.expect
index 2d1371090af..3ed80bfd485 100644
--- a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.outline.expect
+++ b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.outline.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let dynamic #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.expect b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.expect
index 87fc76e26c2..397a76d1c9b 100644
--- a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.expect
+++ b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let dynamic #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.transformed.expect b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.transformed.expect
index 03943113373..2b04ded0b1a 100644
--- a/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/redirecting_factory_const_inference.dart.strong.transformed.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let<BottomType> #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/redirection_type_arguments.dart.outline.expect b/pkg/front_end/testcases/general/redirection_type_arguments.dart.outline.expect
index 41181941707..b15ac8d6d7a 100644
--- a/pkg/front_end/testcases/general/redirection_type_arguments.dart.outline.expect
+++ b/pkg/front_end/testcases/general/redirection_type_arguments.dart.outline.expect
@@ -4,7 +4,7 @@ import "dart:core" as core;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -12,7 +12,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let dynamic #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.expect b/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.expect
index a87fba5fcdb..81c22f9b7e7 100644
--- a/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.expect
+++ b/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let dynamic #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.transformed.expect b/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.transformed.expect
index d6f34c92c48..8c2291db438 100644
--- a/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/redirection_type_arguments.dart.strong.transformed.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let<BottomType> #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.outline.expect b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.outline.expect
index 2b697f3d74d..9c617a6bd45 100644
--- a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.outline.expect
+++ b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.outline.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.expect b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.expect
index 422552b75a8..545b6392d96 100644
--- a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.expect
+++ b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.transformed.expect b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.transformed.expect
index 422552b75a8..545b6392d96 100644
--- a/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/type_literal_as_metadata.dart.strong.transformed.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/type_variable_uses.dart.outline.expect b/pkg/front_end/testcases/general/type_variable_uses.dart.outline.expect
index 6de5e4c8545..4f019701a56 100644
--- a/pkg/front_end/testcases/general/type_variable_uses.dart.outline.expect
+++ b/pkg/front_end/testcases/general/type_variable_uses.dart.outline.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/type_variable_uses.dart.strong.expect b/pkg/front_end/testcases/general/type_variable_uses.dart.strong.expect
index 71db16bf614..8b711958ab4 100644
--- a/pkg/front_end/testcases/general/type_variable_uses.dart.strong.expect
+++ b/pkg/front_end/testcases/general/type_variable_uses.dart.strong.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general/type_variable_uses.dart.strong.transformed.expect b/pkg/front_end/testcases/general/type_variable_uses.dart.strong.transformed.expect
index 71db16bf614..8b711958ab4 100644
--- a/pkg/front_end/testcases/general/type_variable_uses.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/type_variable_uses.dart.strong.transformed.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.outline.expect
index 0d1797b0843..5d802a54288 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.outline.expect
@@ -8,7 +8,7 @@ class DeltaBlue extends core::Object {
   method run() → void
     ;
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -25,7 +25,7 @@ class Strength extends core::Object {
   static method strongest(self::Strength* s1, self::Strength* s2) → self::Strength*
     ;
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.transformed.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.strong.transformed.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.transformed.expect
index 2a91755f9f4..2b67a8a8cb3 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/DeltaBlue.dart.weak.transformed.expect
@@ -11,7 +11,7 @@ class DeltaBlue extends core::Object {
     self::projectionTest(100);
   }
 }
-class Strength extends core::Object {
+class Strength extends core::Object /*hasConstConstructor*/  {
   final field core::int* value;
   final field core::String* name;
   const constructor •(core::int* value, core::String* name) → self::Strength*
@@ -32,7 +32,7 @@ class Strength extends core::Object {
     return self::Strength::stronger(s1, s2) ?{self::Strength*} s1 : s2;
   }
 }
-abstract class Constraint extends core::Object {
+abstract class Constraint extends core::Object /*hasConstConstructor*/  {
   final field self::Strength* strength;
   const constructor •(self::Strength* strength) → self::Constraint*
     : self::Constraint::strength = strength, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.outline.expect
index 4c54d2f6ff6..3a9691adf0c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.outline.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = const <self::Foo*>[self::Foo::bar, self::Foo::baz, self::Foo::cafebabe];
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.transformed.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.strong.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.transformed.expect
index b030b8ae9a0..ad232a9eda1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_on_enum_values.dart.weak.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Fisk<T extends core::Object* = dynamic> extends core::Object {
+class Fisk<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::Fisk::T* x;
   const constructor fisk(self::Fisk::T* x) → self::Fisk<self::Fisk::T*>*
     : self::Fisk::x = x, super core::Object::•()
     ;
 }
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C10;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.outline.expect
index 5fc0262855e..62a6a88c01f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.outline.expect
@@ -6,7 +6,7 @@ import "dart:core" as core;
 
 typedef F1 = () →* void;
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.transformed.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.strong.transformed.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.transformed.expect
index 6f2d3774762..29c9cb7f4df 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_top.dart.weak.transformed.expect
@@ -10,7 +10,7 @@ typedef F1 = () →* void;
 @#C1
 @#C2
 typedef F2 = () →* void;
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* value) → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.outline.expect
index 368f1dd9af0..86cd7acdc72 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({named: dynamic}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.transformed.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.transformed.expect
index 023576ca772..7a689b8e390 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/annotation_variable_declaration.dart.weak.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef hest_t = ({@#C1 dynamic named}) →* dynamic;
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.outline.expect
index 6dcbef20ef3..193fcfdbf8f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.outline.expect
@@ -174,7 +174,7 @@ class Ei<T extends core::Object* = dynamic> = core::Object with self::Empty {
   synthetic constructor •() → self::Ei<self::Ei::T*>*
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -183,7 +183,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
   synthetic constructor •() → self::F<self::F::T*>*
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
   synthetic constructor •() → self::Fc<self::Fc::T*>*
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -201,7 +201,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
   synthetic constructor •() → self::Fi<self::Fi::T*>*
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     ;
 }
@@ -209,7 +209,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
   synthetic constructor •() → self::G<self::G::T*>*
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     ;
 }
@@ -217,7 +217,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
   synthetic constructor •() → self::Gc<self::Gc::T*>*
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     ;
 }
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.expect
index d928707ca97..f823e7b132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.expect
@@ -185,7 +185,7 @@ class Ei<T extends core::Object* = dynamic> = core::Object with self::Empty {
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
index cf7a1fe21db..7ca9c2ac830 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.strong.transformed.expect
@@ -170,22 +170,22 @@ class Di<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::E<self::E::T*>*
     : super core::Object::•()
     ;
 }
-class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ec<self::Ec::T*>*
     : super core::Object::•()
     ;
 }
-class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ei<self::Ei::T*>*
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.expect
index d928707ca97..f823e7b132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.expect
@@ -185,7 +185,7 @@ class Ei<T extends core::Object* = dynamic> = core::Object with self::Empty {
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> = core::Object with self::Empty /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.transformed.expect
index cf7a1fe21db..7ca9c2ac830 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bad_type_variable_uses_in_supertypes.dart.weak.transformed.expect
@@ -170,22 +170,22 @@ class Di<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class E<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::E<self::E::T*>*
     : super core::Object::•()
     ;
 }
-class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ec<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ec<self::Ec::T*>*
     : super core::Object::•()
     ;
 }
-class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+class Ei<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Ei<self::Ei::T*>*
     : super core::Object::•()
     ;
 }
-abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _F&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_F&Object&A<self::_F&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -195,7 +195,7 @@ class F<T extends core::Object* = dynamic> extends self::_F&Object&A<self::F::T*
     : super self::_F&Object&A::•()
     ;
 }
-abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fc&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fc&Object&A<self::_Fc&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -205,7 +205,7 @@ class Fc<T extends core::Object* = dynamic> extends self::_Fc&Object&A<self::Fc:
     : super self::_Fc&Object&A::•()
     ;
 }
-abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object {
+abstract class _Fi&Object&A<T extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fi&Object&A<self::_Fi&Object&A::T*>*
     : super core::Object::•()
     ;
@@ -215,7 +215,7 @@ class Fi<T extends core::Object* = dynamic> extends self::_Fi&Object&A<self::Fi:
     : super self::_Fi&Object&A::•()
     ;
 }
-abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _G&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_G&A&Empty<self::_G&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -225,7 +225,7 @@ class G<T extends core::Object* = dynamic> extends self::_G&A&Empty<self::G::T*>
     : super self::_G&A&Empty::•()
     ;
 }
-abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gc&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gc&A&Empty<self::_Gc&A&Empty::T*>*
     : super core::Object::•()
     ;
@@ -235,7 +235,7 @@ class Gc<T extends core::Object* = dynamic> extends self::_Gc&A&Empty<self::Gc::
     : super self::_Gc&A&Empty::•()
     ;
 }
-abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty {
+abstract class _Gi&A&Empty<T extends core::Object* = dynamic> extends core::Object implements self::Empty /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Gi&A&Empty<self::_Gi&A&Empty::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.outline.expect
index 511a3f479b7..8274b912cc2 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.outline.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   method foo() → void
     ;
 }
-abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
+abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.expect
index 98cc4a6a675..7bed64471a9 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
+abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.transformed.expect
index f56cb2a4371..6cd473f3ab0 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.strong.transformed.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest {
+abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.expect
index 98cc4a6a675..7bed64471a9 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
+abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.transformed.expect
index f56cb2a4371..6cd473f3ab0 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug33099.dart.weak.transformed.expect
@@ -5,7 +5,7 @@ import "dart:mirrors" as mir;
 
 import "dart:mirrors";
 
-class _FailingTest extends core::Object {
+class _FailingTest extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_FailingTest*
     : super core::Object::•()
     ;
@@ -17,7 +17,7 @@ class MyTest extends core::Object {
   @#C1
   method foo() → void {}
 }
-abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest {
+abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_MyTest2&Object&MyTest*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.outline.expect
index cf7dcd39acb..494ce669ad1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.outline.expect
@@ -6,7 +6,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
   synthetic constructor •() → self::A<self::A::X*>*
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.expect
index f743320677e..4de7d7edd42 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.transformed.expect
index 534c2d32ae5..ffac059549c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.strong.transformed.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.expect
index f743320677e..4de7d7edd42 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> = core::Object with self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.transformed.expect
index 534c2d32ae5..ffac059549c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/bug34511.dart.weak.transformed.expect
@@ -7,7 +7,7 @@ class A<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> {
+abstract class _B&Object&A<Z extends core::Object* = dynamic> extends core::Object implements self::A<() →* self::_B&Object&A::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.outline.expect
index 4c7789d4784..e4929d58198 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.outline.expect
@@ -111,7 +111,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
   synthetic constructor •() → self::Am1<self::Am1::X*, self::Am1::Y*>*
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -120,7 +120,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
   synthetic constructor •() → self::Bm1<self::Bm1::Z*>*
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -129,7 +129,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
   synthetic constructor •() → self::Cm1<self::Cm1::Z*>*
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -138,7 +138,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
   synthetic constructor •() → self::Dm1<self::Dm1::Z*>*
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -147,7 +147,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
   synthetic constructor •() → self::Em1<self::Em1::Z*>*
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -156,7 +156,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
   synthetic constructor •() → self::Fm1<self::Fm1::Z*>*
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -165,7 +165,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
   synthetic constructor •() → self::Gm1<self::Gm1::Z*>*
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -174,7 +174,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
   synthetic constructor •() → self::Hm1<self::Hm1::Z*>*
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -183,7 +183,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
   synthetic constructor •() → self::Im1<self::Im1::Z*>*
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
   synthetic constructor •() → self::Jm1<self::Jm1::Z*>*
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -201,7 +201,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
   synthetic constructor •() → self::Km1<self::Km1::Z*>*
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -269,7 +269,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
   synthetic constructor •() → self::Am2<self::Am2::X*, self::Am2::Y*>*
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -278,7 +278,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
   synthetic constructor •() → self::Bm2<self::Bm2::Z*>*
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -287,7 +287,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
   synthetic constructor •() → self::Cm2<self::Cm2::Z*>*
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -296,7 +296,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
   synthetic constructor •() → self::Dm2<self::Dm2::Z*>*
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -305,7 +305,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
   synthetic constructor •() → self::Em2<self::Em2::Z*>*
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -314,7 +314,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
   synthetic constructor •() → self::Fm2<self::Fm2::Z*>*
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -323,7 +323,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
   synthetic constructor •() → self::Gm2<self::Gm2::Z*>*
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
   synthetic constructor •() → self::Hm2<self::Hm2::Z*>*
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -341,7 +341,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
   synthetic constructor •() → self::Im2<self::Im2::Z*>*
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -350,7 +350,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
   synthetic constructor •() → self::Jm2<self::Jm2::Z*>*
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -359,7 +359,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
   synthetic constructor •() → self::Km2<self::Km2::Z*>*
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -427,7 +427,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
   synthetic constructor •() → self::Am3<self::Am3::L*, self::Am3::Y*>*
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -436,7 +436,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
   synthetic constructor •() → self::Bm3<self::Bm3::Z*>*
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -445,7 +445,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
   synthetic constructor •() → self::Cm3<self::Cm3::Z*>*
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -454,7 +454,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
   synthetic constructor •() → self::Dm3<self::Dm3::Z*>*
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -463,7 +463,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
   synthetic constructor •() → self::Em3<self::Em3::Z*>*
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
   synthetic constructor •() → self::Fm3<self::Fm3::Z*>*
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -481,7 +481,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
   synthetic constructor •() → self::Gm3<self::Gm3::Z*>*
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -490,7 +490,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
   synthetic constructor •() → self::Hm3<self::Hm3::Z*>*
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -499,7 +499,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
   synthetic constructor •() → self::Im3<self::Im3::Z*>*
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -508,7 +508,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
   synthetic constructor •() → self::Jm3<self::Jm3::Z*>*
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.expect
index 08e48dbb799..1d8753ef256 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.transformed.expect
index e8aa8a5200a..cae8d00d3c1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.strong.transformed.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -222,57 +222,57 @@ class Lm1<Z extends core::Object* = dynamic> extends self::_Lm1&Object&Am1<self:
     : super self::_Lm1&Object&Am1::•()
     ;
 }
-class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> {
+class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm1<self::Mm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> {
+class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm1<self::Nm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> {
+class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om1<self::Om1::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> {
+class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm1<self::Pm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> {
+class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm1<self::Qm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> {
+class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm1<self::Rm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> {
+class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm1<self::Sm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> {
+class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm1<self::Tm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> {
+class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um1<self::Um1::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> {
+class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm1<self::Vm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> {
+class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm1<self::Wm1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -392,57 +392,57 @@ class Lm2<Z extends core::Object* = dynamic> extends self::_Lm2&Object&Am2<self:
     : super self::_Lm2&Object&Am2::•()
     ;
 }
-class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> {
+class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm2<self::Mm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> {
+class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm2<self::Nm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> {
+class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om2<self::Om2::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> {
+class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm2<self::Pm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> {
+class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm2<self::Qm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> {
+class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm2<self::Rm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> {
+class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm2<self::Sm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> {
+class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm2<self::Tm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> {
+class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um2<self::Um2::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> {
+class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm2<self::Vm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> {
+class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm2<self::Wm2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.expect
index 08e48dbb799..1d8753ef256 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> = core::Object with self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> = core::Object with self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> = core::Object with self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.transformed.expect
index e8aa8a5200a..cae8d00d3c1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/clone_function_type.dart.weak.transformed.expect
@@ -112,7 +112,7 @@ class Am1<X extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> {
+abstract class _Bm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Bm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm1&Object&Am1<self::_Bm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -122,7 +122,7 @@ class Bm1<Z extends core::Object* = dynamic> extends self::_Bm1&Object&Am1<self:
     : super self::_Bm1&Object&Am1::•()
     ;
 }
-abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> {
+abstract class _Cm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::_Cm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm1&Object&Am1<self::_Cm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -132,7 +132,7 @@ class Cm1<Z extends core::Object* = dynamic> extends self::_Cm1&Object&Am1<self:
     : super self::_Cm1&Object&Am1::•()
     ;
 }
-abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> {
+abstract class _Dm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::_Dm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm1&Object&Am1<self::_Dm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -142,7 +142,7 @@ class Dm1<Z extends core::Object* = dynamic> extends self::_Dm1&Object&Am1<self:
     : super self::_Dm1&Object&Am1::•()
     ;
 }
-abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> {
+abstract class _Em1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Em1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em1&Object&Am1<self::_Em1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -152,7 +152,7 @@ class Em1<Z extends core::Object* = dynamic> extends self::_Em1&Object&Am1<self:
     : super self::_Em1&Object&Am1::•()
     ;
 }
-abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> {
+abstract class _Fm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::_Fm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm1&Object&Am1<self::_Fm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -162,7 +162,7 @@ class Fm1<Z extends core::Object* = dynamic> extends self::_Fm1&Object&Am1<self:
     : super self::_Fm1&Object&Am1::•()
     ;
 }
-abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> {
+abstract class _Gm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::_Gm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm1&Object&Am1<self::_Gm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -172,7 +172,7 @@ class Gm1<Z extends core::Object* = dynamic> extends self::_Gm1&Object&Am1<self:
     : super self::_Gm1&Object&Am1::•()
     ;
 }
-abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> {
+abstract class _Hm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Hm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm1&Object&Am1<self::_Hm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -182,7 +182,7 @@ class Hm1<Z extends core::Object* = dynamic> extends self::_Hm1&Object&Am1<self:
     : super self::_Hm1&Object&Am1::•()
     ;
 }
-abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> {
+abstract class _Im1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::_Im1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im1&Object&Am1<self::_Im1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -192,7 +192,7 @@ class Im1<Z extends core::Object* = dynamic> extends self::_Im1&Object&Am1<self:
     : super self::_Im1&Object&Am1::•()
     ;
 }
-abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> {
+abstract class _Jm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::_Jm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm1&Object&Am1<self::_Jm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -202,7 +202,7 @@ class Jm1<Z extends core::Object* = dynamic> extends self::_Jm1&Object&Am1<self:
     : super self::_Jm1&Object&Am1::•()
     ;
 }
-abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> {
+abstract class _Km1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::_Km1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km1&Object&Am1<self::_Km1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -212,7 +212,7 @@ class Km1<Z extends core::Object* = dynamic> extends self::_Km1&Object&Am1<self:
     : super self::_Km1&Object&Am1::•()
     ;
 }
-abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> {
+abstract class _Lm1&Object&Am1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::_Lm1&Object&Am1::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm1&Object&Am1<self::_Lm1&Object&Am1::Z*>*
     : super core::Object::•()
     ;
@@ -222,57 +222,57 @@ class Lm1<Z extends core::Object* = dynamic> extends self::_Lm1&Object&Am1<self:
     : super self::_Lm1&Object&Am1::•()
     ;
 }
-class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> {
+class Mm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Mm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm1<self::Mm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> {
+class Nm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::int*) →* dynamic, self::Nm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm1<self::Nm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> {
+class Om1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* core::int*, self::Om1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om1<self::Om1::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> {
+class Pm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Pm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm1<self::Pm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> {
+class Qm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* dynamic, self::Qm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm1<self::Qm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> {
+class Rm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<({x: core::int*}) →* dynamic, self::Rm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm1<self::Rm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> {
+class Sm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Sm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm1<self::Sm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> {
+class Tm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<([core::int*]) →* dynamic, self::Tm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm1<self::Tm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> {
+class Um1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<core::Function*, self::Um1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um1<self::Um1::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> {
+class Vm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<(core::Function*) →* dynamic, self::Vm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm1<self::Vm1::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> {
+class Wm1<Z extends core::Object* = dynamic> extends core::Object implements self::Am1<() →* (() →* core::Function*) →* dynamic, self::Wm1::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm1<self::Wm1::Z*>*
     : super core::Object::•()
     ;
@@ -282,7 +282,7 @@ class Am2<X extends () →* dynamic = () →* dynamic, Y extends core::Object* =
     : super core::Object::•()
     ;
 }
-abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> {
+abstract class _Bm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Bm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm2&Object&Am2<self::_Bm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -292,7 +292,7 @@ class Bm2<Z extends core::Object* = dynamic> extends self::_Bm2&Object&Am2<self:
     : super self::_Bm2&Object&Am2::•()
     ;
 }
-abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> {
+abstract class _Cm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::_Cm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm2&Object&Am2<self::_Cm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -302,7 +302,7 @@ class Cm2<Z extends core::Object* = dynamic> extends self::_Cm2&Object&Am2<self:
     : super self::_Cm2&Object&Am2::•()
     ;
 }
-abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> {
+abstract class _Dm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::_Dm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm2&Object&Am2<self::_Dm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -312,7 +312,7 @@ class Dm2<Z extends core::Object* = dynamic> extends self::_Dm2&Object&Am2<self:
     : super self::_Dm2&Object&Am2::•()
     ;
 }
-abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> {
+abstract class _Em2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Em2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em2&Object&Am2<self::_Em2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -322,7 +322,7 @@ class Em2<Z extends core::Object* = dynamic> extends self::_Em2&Object&Am2<self:
     : super self::_Em2&Object&Am2::•()
     ;
 }
-abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> {
+abstract class _Fm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::_Fm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm2&Object&Am2<self::_Fm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -332,7 +332,7 @@ class Fm2<Z extends core::Object* = dynamic> extends self::_Fm2&Object&Am2<self:
     : super self::_Fm2&Object&Am2::•()
     ;
 }
-abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> {
+abstract class _Gm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::_Gm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm2&Object&Am2<self::_Gm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -342,7 +342,7 @@ class Gm2<Z extends core::Object* = dynamic> extends self::_Gm2&Object&Am2<self:
     : super self::_Gm2&Object&Am2::•()
     ;
 }
-abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> {
+abstract class _Hm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Hm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm2&Object&Am2<self::_Hm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -352,7 +352,7 @@ class Hm2<Z extends core::Object* = dynamic> extends self::_Hm2&Object&Am2<self:
     : super self::_Hm2&Object&Am2::•()
     ;
 }
-abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> {
+abstract class _Im2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::_Im2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im2&Object&Am2<self::_Im2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -362,7 +362,7 @@ class Im2<Z extends core::Object* = dynamic> extends self::_Im2&Object&Am2<self:
     : super self::_Im2&Object&Am2::•()
     ;
 }
-abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> {
+abstract class _Jm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::_Jm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm2&Object&Am2<self::_Jm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -372,7 +372,7 @@ class Jm2<Z extends core::Object* = dynamic> extends self::_Jm2&Object&Am2<self:
     : super self::_Jm2&Object&Am2::•()
     ;
 }
-abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> {
+abstract class _Km2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::_Km2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km2&Object&Am2<self::_Km2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -382,7 +382,7 @@ class Km2<Z extends core::Object* = dynamic> extends self::_Km2&Object&Am2<self:
     : super self::_Km2&Object&Am2::•()
     ;
 }
-abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> {
+abstract class _Lm2&Object&Am2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::_Lm2&Object&Am2::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Lm2&Object&Am2<self::_Lm2&Object&Am2::Z*>*
     : super core::Object::•()
     ;
@@ -392,57 +392,57 @@ class Lm2<Z extends core::Object* = dynamic> extends self::_Lm2&Object&Am2<self:
     : super self::_Lm2&Object&Am2::•()
     ;
 }
-class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> {
+class Mm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Mm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Mm2<self::Mm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> {
+class Nm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::int*) →* dynamic, self::Nm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Nm2<self::Nm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> {
+class Om2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* core::int*, self::Om2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Om2<self::Om2::Z*>*
     : super core::Object::•()
     ;
 }
-class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> {
+class Pm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Pm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Pm2<self::Pm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> {
+class Qm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* dynamic, self::Qm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Qm2<self::Qm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> {
+class Rm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<({x: core::int*}) →* dynamic, self::Rm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Rm2<self::Rm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> {
+class Sm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Sm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Sm2<self::Sm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> {
+class Tm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<([core::int*]) →* dynamic, self::Tm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Tm2<self::Tm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> {
+class Um2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<core::Function*, self::Um2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Um2<self::Um2::Z*>*
     : super core::Object::•()
     ;
 }
-class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> {
+class Vm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<(core::Function*) →* dynamic, self::Vm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Vm2<self::Vm2::Z*>*
     : super core::Object::•()
     ;
 }
-class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> {
+class Wm2<Z extends core::Object* = dynamic> extends core::Object implements self::Am2<() →* (() →* core::Function*) →* dynamic, self::Wm2::Z*> /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Wm2<self::Wm2::Z*>*
     : super core::Object::•()
     ;
@@ -452,7 +452,7 @@ class Am3<L extends core::Object* = dynamic, Y extends core::Object* = dynamic>
     : super core::Object::•()
     ;
 }
-abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> {
+abstract class _Bm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Bm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Bm3&Object&Am3<self::_Bm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -462,7 +462,7 @@ class Bm3<Z extends core::Object* = dynamic> extends self::_Bm3&Object&Am3<self:
     : super self::_Bm3&Object&Am3::•()
     ;
 }
-abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> {
+abstract class _Cm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::int*) →* dynamic, self::_Cm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Cm3&Object&Am3<self::_Cm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -472,7 +472,7 @@ class Cm3<Z extends core::Object* = dynamic> extends self::_Cm3&Object&Am3<self:
     : super self::_Cm3&Object&Am3::•()
     ;
 }
-abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> {
+abstract class _Dm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* core::int*, self::_Dm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Dm3&Object&Am3<self::_Dm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -482,7 +482,7 @@ class Dm3<Z extends core::Object* = dynamic> extends self::_Dm3&Object&Am3<self:
     : super self::_Dm3&Object&Am3::•()
     ;
 }
-abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> {
+abstract class _Em3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Em3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Em3&Object&Am3<self::_Em3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -492,7 +492,7 @@ class Em3<Z extends core::Object* = dynamic> extends self::_Em3&Object&Am3<self:
     : super self::_Em3&Object&Am3::•()
     ;
 }
-abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> {
+abstract class _Fm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* dynamic, self::_Fm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Fm3&Object&Am3<self::_Fm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -502,7 +502,7 @@ class Fm3<Z extends core::Object* = dynamic> extends self::_Fm3&Object&Am3<self:
     : super self::_Fm3&Object&Am3::•()
     ;
 }
-abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> {
+abstract class _Gm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<({x: core::int*}) →* dynamic, self::_Gm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Gm3&Object&Am3<self::_Gm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -512,7 +512,7 @@ class Gm3<Z extends core::Object* = dynamic> extends self::_Gm3&Object&Am3<self:
     : super self::_Gm3&Object&Am3::•()
     ;
 }
-abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> {
+abstract class _Hm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Hm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hm3&Object&Am3<self::_Hm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -522,7 +522,7 @@ class Hm3<Z extends core::Object* = dynamic> extends self::_Hm3&Object&Am3<self:
     : super self::_Hm3&Object&Am3::•()
     ;
 }
-abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> {
+abstract class _Im3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<([core::int*]) →* dynamic, self::_Im3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Im3&Object&Am3<self::_Im3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -532,7 +532,7 @@ class Im3<Z extends core::Object* = dynamic> extends self::_Im3&Object&Am3<self:
     : super self::_Im3&Object&Am3::•()
     ;
 }
-abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> {
+abstract class _Jm3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<(core::Function*) →* dynamic, self::_Jm3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Jm3&Object&Am3<self::_Jm3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
@@ -542,7 +542,7 @@ class Jm3<Z extends core::Object* = dynamic> extends self::_Jm3&Object&Am3<self:
     : super self::_Jm3&Object&Am3::•()
     ;
 }
-abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> {
+abstract class _Km3&Object&Am3<Z extends core::Object* = dynamic> extends core::Object implements self::Am3<() →* (() →* core::Function*) →* dynamic, self::_Km3&Object&Am3::Z*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Km3&Object&Am3<self::_Km3&Object&Am3::Z*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.outline.expect
index b358ba85417..464c765df1a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.outline.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.expect
index 3ce1d82c6b3..04ddb74e3d5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
index 3ce1d82c6b3..04ddb74e3d5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.strong.transformed.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.expect
index 3ce1d82c6b3..04ddb74e3d5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.transformed.expect
index 3ce1d82c6b3..04ddb74e3d5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/co19_language_metadata_syntax_t04.dart.weak.transformed.expect
@@ -16,7 +16,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.outline.expect
index 77754c20f73..aef74b26e5a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.outline.expect
@@ -9,14 +9,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.expect
index b4fdfe821a0..13e83242a5e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.transformed.expect
index b4fdfe821a0..13e83242a5e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.strong.transformed.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.expect
index b4fdfe821a0..13e83242a5e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.transformed.expect
index b4fdfe821a0..13e83242a5e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/const_redirect_to_nonconst.dart.weak.transformed.expect
@@ -13,14 +13,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : this self::A::bad()
     ;
   constructor bad() → self::A*
     : super core::Object::•() {}
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : super self::A::bad()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.outline.expect
index 6cda74d5595..934d099c09c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.transformed.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.transformed.expect
index c95b9b295cc..117976825ff 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/constructor_const_inference.dart.weak.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class _Y<T extends core::Object* = dynamic> extends core::Object {
+class _Y<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.outline.expect
index d71903cdf5e..a5ac2794384 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.outline.expect
@@ -13,5 +13,5 @@ static method test() → dynamic
 static method main() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.expect
index 0de8c13ad19..554df33e7eb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.expect
@@ -33,5 +33,5 @@ Try correcting the name to the name of an existing method, or defining a method
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.transformed.expect
index 0de8c13ad19..554df33e7eb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.strong.transformed.expect
@@ -33,5 +33,5 @@ Try correcting the name to the name of an existing method, or defining a method
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.expect
index 0de8c13ad19..554df33e7eb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.expect
@@ -33,5 +33,5 @@ Try correcting the name to the name of an existing method, or defining a method
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.transformed.expect
index 0de8c13ad19..554df33e7eb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/continue_inference_after_error.dart.weak.transformed.expect
@@ -33,5 +33,5 @@ Try correcting the name to the name of an existing method, or defining a method
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
index d8dce848e5c..f2001a3c182 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.outline.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
   method foo(core::num* x) → void
     ;
 }
-abstract class _D&A&B = self::A with self::B {
+abstract class _D&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
index 08d745d6180..03d861d3c7a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B = self::A with self::B {
+abstract class _D&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
index 24f8755123a..b35ef09c679 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B extends self::A implements self::B {
+abstract class _D&A&B extends self::A implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.expect
index 08d745d6180..03d861d3c7a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B = self::A with self::B {
+abstract class _D&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.transformed.expect
index 24f8755123a..b35ef09c679 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/covariant_parameter_in_superclass_of_mixin_application.dart.weak.transformed.expect
@@ -20,7 +20,7 @@ class C extends core::Object {
     ;
   method foo(core::num* x) → void {}
 }
-abstract class _D&A&B extends self::A implements self::B {
+abstract class _D&A&B extends self::A implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_D&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.outline.expect
index 274daea20ea..7865d47eba1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.outline.expect
@@ -359,7 +359,7 @@ class Sub extends core::Object {
   method m() → dynamic
     ;
 }
-class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#4 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#4*>* values = const <self::Enum#4*>[self::Enum#4::a];
@@ -370,7 +370,7 @@ class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#4::_name};
 }
-class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#3 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#3*>* values = const <self::Enum#3*>[self::Enum#3::a, self::Enum#3::b, self::Enum#3::c];
@@ -383,7 +383,7 @@ class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#3::_name};
 }
-class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#2 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#2*>* values = const <self::Enum#2*>[self::Enum#2::Enum, self::Enum#2::a, self::Enum#2::b];
@@ -396,7 +396,7 @@ class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#2::_name};
 }
-class Enum#1 extends core::Object {
+class Enum#1 extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#1*>* values = const <self::Enum#1*>[self::Enum#1::a, self::Enum#1::b, self::Enum#1::c];
@@ -409,7 +409,7 @@ class Enum#1 extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum#1::_name};
 }
-class Enum extends core::Object {
+class Enum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum*>* values = const <self::Enum*>[self::Enum::Enum, self::Enum::a, self::Enum::b];
@@ -422,7 +422,7 @@ class Enum extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum::_name};
 }
-class AnotherEnum extends core::Object {
+class AnotherEnum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::AnotherEnum*>* values = const <self::AnotherEnum*>[self::AnotherEnum::a, self::AnotherEnum::b, self::AnotherEnum::c];
@@ -443,5 +443,5 @@ static method foo() → dynamic
 static method useAnotherEnum() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.strong.expect
index 1995e4597cc..91565864098 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.strong.expect
@@ -421,7 +421,7 @@ Try removing the extra positional arguments.
   method m() → dynamic
     return super.m();
 }
-class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#4 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#4*>* values = #C4;
@@ -432,7 +432,7 @@ class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#4::_name};
 }
-class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#3 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#3*>* values = #C12;
@@ -445,7 +445,7 @@ class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#3::_name};
 }
-class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#2 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#2*>* values = #C17;
@@ -458,7 +458,7 @@ class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#2::_name};
 }
-class Enum#1 extends core::Object {
+class Enum#1 extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#1*>* values = #C21;
@@ -471,7 +471,7 @@ class Enum#1 extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum#1::_name};
 }
-class Enum extends core::Object {
+class Enum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum*>* values = #C25;
@@ -484,7 +484,7 @@ class Enum extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum::_name};
 }
-class AnotherEnum extends core::Object {
+class AnotherEnum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::AnotherEnum*>* values = #C32;
@@ -524,7 +524,7 @@ static method useAnotherEnum() → dynamic {
                                       ^^^^^^"};
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
 
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.weak.expect
index 1995e4597cc..91565864098 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/duplicated_declarations.dart.weak.expect
@@ -421,7 +421,7 @@ Try removing the extra positional arguments.
   method m() → dynamic
     return super.m();
 }
-class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#4 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#4*>* values = #C4;
@@ -432,7 +432,7 @@ class Enum#4 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#4::_name};
 }
-class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#3 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#3*>* values = #C12;
@@ -445,7 +445,7 @@ class Enum#3 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#3::_name};
 }
-class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_declarations_part.dart
+class Enum#2 extends core::Object /*isEnum*/  { // from org-dartlang-testcase:///duplicated_declarations_part.dart
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#2*>* values = #C17;
@@ -458,7 +458,7 @@ class Enum#2 extends core::Object { // from org-dartlang-testcase:///duplicated_
   method toString() → core::String*
     return this.{=self::Enum#2::_name};
 }
-class Enum#1 extends core::Object {
+class Enum#1 extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum#1*>* values = #C21;
@@ -471,7 +471,7 @@ class Enum#1 extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum#1::_name};
 }
-class Enum extends core::Object {
+class Enum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Enum*>* values = #C25;
@@ -484,7 +484,7 @@ class Enum extends core::Object {
   method toString() → core::String*
     return this.{=self::Enum::_name};
 }
-class AnotherEnum extends core::Object {
+class AnotherEnum extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::AnotherEnum*>* values = #C32;
@@ -524,7 +524,7 @@ static method useAnotherEnum() → dynamic {
                                       ^^^^^^"};
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
 
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.outline.expect
index 14fe62f7bbe..1e369aeb5c4 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.outline.expect
@@ -11,7 +11,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.expect
index dbb3734a963..96b90635efb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.transformed.expect
index dbb3734a963..96b90635efb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.expect
index dbb3734a963..96b90635efb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.transformed.expect
index dbb3734a963..96b90635efb 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_01.dart.weak.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.outline.expect
index 25620a04c20..15ae178db74 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.outline.expect
@@ -12,7 +12,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.expect
index da20cdc2968..20a4147f10d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.transformed.expect
index da20cdc2968..20a4147f10d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.strong.transformed.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.expect
index da20cdc2968..20a4147f10d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.transformed.expect
index da20cdc2968..20a4147f10d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_02.dart.weak.transformed.expect
@@ -39,7 +39,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.outline.expect
index e2689c9be02..8e00ee1e1d0 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.outline.expect
@@ -12,7 +12,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.expect
index c2cb3bc18d5..442f52e7916 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.transformed.expect
index c2cb3bc18d5..442f52e7916 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.strong.transformed.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.expect
index c2cb3bc18d5..442f52e7916 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.transformed.expect
index c2cb3bc18d5..442f52e7916 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_03.dart.weak.transformed.expect
@@ -40,7 +40,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.outline.expect
index 4034b8b04d7..8406a72d0a7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.outline.expect
@@ -11,7 +11,7 @@ library;
 import self as self2;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → self2::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -26,7 +26,7 @@ import "error_location_04_lib1.dart" as self2;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field self2::Foo* x;
   const constructor •() → self3::Bar*
     : self3::Bar::x = const self2::Foo::•(0), super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.expect
index 6370a9cdb83..298d70dd3a1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.transformed.expect
index 6370a9cdb83..298d70dd3a1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.expect
index 6370a9cdb83..298d70dd3a1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.transformed.expect
index 6370a9cdb83..298d70dd3a1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/error_locations/error_location_04.dart.weak.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as err;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::int* i) → err::Foo*
     : assert(i.{core::num::>}(0)), super core::Object::•()
     ;
@@ -41,7 +41,7 @@ import "error_location_04_lib1.dart" as err;
 
 import "org-dartlang-testcase:///error_location_04_lib1.dart";
 
-class Bar extends core::Object {
+class Bar extends core::Object /*hasConstConstructor*/  {
   final field err::Foo* x;
   const constructor •() → err2::Bar*
     : err2::Bar::x = invalid-expression "This assertion failed.", super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.outline.expect
index 5506b332f23..239f404d41a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.outline.expect
@@ -21,9 +21,9 @@ class SuperClass extends core::Object {
   synthetic constructor •() → self::SuperClass*
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     ;
 }
@@ -31,7 +31,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
   synthetic constructor •() → self::Class1<self::Class1::T*, self::Class1::S*>*
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.expect
index 6053acb6e5c..2f4e9b75556 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.transformed.expect
index 027d8c96b66..5e785864f0b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.strong.transformed.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.expect
index 6053acb6e5c..2f4e9b75556 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> = core::Object with self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.transformed.expect
index 027d8c96b66..5e785864f0b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/extend_with_type_variable.dart.weak.transformed.expect
@@ -22,9 +22,9 @@ class SuperClass extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Mixin<T extends core::Object* = dynamic> extends core::Object {
+abstract class Mixin<T extends core::Object* = dynamic> extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> {
+abstract class _Class1&S&Mixin<T extends core::Object* = dynamic, S extends self::SuperClass* = self::SuperClass*> extends core::Object implements self::Mixin<self::_Class1&S&Mixin::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Class1&S&Mixin<self::_Class1&S&Mixin::T*, self::_Class1&S&Mixin::S*>*
     : super core::Object::•()
     ;
@@ -34,7 +34,7 @@ class Class1<T extends core::Object* = dynamic, S extends self::SuperClass* = se
     : super self::_Class1&S&Mixin::•()
     ;
 }
-abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass {
+abstract class _Class2&SuperClass&M<T extends core::Object* = dynamic, M extends self::Mixin<self::_Class2&SuperClass&M::T*>* = self::Mixin<dynamic>*> extends self::SuperClass /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Class2&SuperClass&M<self::_Class2&SuperClass&M::T*, self::_Class2&SuperClass&M::M*>*
     : super self::SuperClass::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.outline.expect
index b0af5d4b3ed..700f57e4953 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.outline.expect
@@ -1,7 +1,7 @@
 @dart._internal::ExternalName::•("dart-ext:here")
 @dart._internal::ExternalName::•("dart-ext:foo/../there")
 @dart._internal::ExternalName::•("dart-ext:/usr/local/somewhere")
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:_internal" as _in;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.expect
index 92724dc89cf..8379e80a14f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.expect
@@ -1,7 +1,7 @@
 @#C2
 @#C4
 @#C6
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:_internal" as _in;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.transformed.expect
index 92724dc89cf..8379e80a14f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.strong.transformed.expect
@@ -1,7 +1,7 @@
 @#C2
 @#C4
 @#C6
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:_internal" as _in;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.expect
index 92724dc89cf..8379e80a14f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.expect
@@ -1,7 +1,7 @@
 @#C2
 @#C4
 @#C6
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:_internal" as _in;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.transformed.expect
index 92724dc89cf..8379e80a14f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/external_import.dart.weak.transformed.expect
@@ -1,7 +1,7 @@
 @#C2
 @#C4
 @#C6
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:_internal" as _in;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.outline.expect
index 55f17dd45a5..503d2efd079 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = 87;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.transformed.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.transformed.expect
index c87d93f8266..0c80488a886 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/implicit_const_with_static_fields.dart.weak.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static const field core::int* constField = #C1;
   const constructor •(dynamic x) → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.outline.expect
index ace49f2741a..458f1a0348a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.outline.expect
@@ -12,12 +12,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.expect
index 654cbbe85b8..ed380d18e7d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.transformed.expect
index 654cbbe85b8..ed380d18e7d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.strong.transformed.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.expect
index 654cbbe85b8..ed380d18e7d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.transformed.expect
index 654cbbe85b8..ed380d18e7d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue37776.dart.weak.transformed.expect
@@ -16,12 +16,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class X#1 extends core::Object {
+class X#1 extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X#1*
     : super core::Object::•()
     ;
 }
-class X extends core::Object {
+class X extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::X*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.outline.expect
index b4885811582..23b193701c7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.outline.expect
@@ -13,7 +13,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
   synthetic constructor •() → self::A<self::A::Q*>*
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.expect
index 3c42fc9780e..7473a3480c7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.transformed.expect
index 3c42fc9780e..7473a3480c7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.strong.transformed.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.expect
index 3c42fc9780e..7473a3480c7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.transformed.expect
index 3c42fc9780e..7473a3480c7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/issue38944.dart.weak.transformed.expect
@@ -14,7 +14,7 @@ class A<Q extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object {
+abstract class _B&Object&A<X extends core::Object* = dynamic> extends core::Object /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::X*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.outline.expect
index 02428e5063f..9eab40cfac7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.expect
index 41215f551e2..5ded87e132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.transformed.expect
index 41215f551e2..5ded87e132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.strong.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.expect
index 41215f551e2..5ded87e132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.transformed.expect
index 41215f551e2..5ded87e132e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/magic_const.dart.weak.transformed.expect
@@ -25,7 +25,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Constant extends core::Object {
+class Constant extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Constant*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.outline.expect
index e16a9e13a8c..6d4eac1b997 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.outline.expect
@@ -30,7 +30,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     ;
@@ -50,7 +50,7 @@ class C extends core::Object {
   synthetic constructor •() → self::C*
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.expect
index dd6951ed4f4..39a61d25815 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:10:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.transformed.expect
index dd6951ed4f4..39a61d25815 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.strong.transformed.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:10:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
index dd6951ed4f4..39a61d25815 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:10:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
index dd6951ed4f4..39a61d25815 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
@@ -53,7 +53,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field dynamic x = null;
   constructor named1() → self::A*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:10:26: Error: Constructor bodies can't use 'async', 'async*', or 'sync*'.
@@ -77,7 +77,7 @@ class C extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class AbstractClass extends core::Object {
+abstract class AbstractClass extends core::Object /*hasConstConstructor*/  {
   const constructor id() → self::AbstractClass*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.outline.expect
index 7c3363ef06e..8944460c5b5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @self::a
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = const <self::E*>[self::E::E1, self::E::E2, self::E::E3];
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.transformed.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.transformed.expect
index 676b3551620..623dc088c68 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_enum.dart.weak.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C11;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.strong.transformed.expect
index 5cd563596cf..1b24fb63151 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class C extends self::D implements self::E {
+class C extends self::D implements self::E /*isEliminatedMixin*/  {
   synthetic constructor •() → self::C*
     : super self::D::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.weak.transformed.expect
index 5cd563596cf..1b24fb63151 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/metadata_named_mixin_application.dart.weak.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 @#C1
-class C extends self::D implements self::E {
+class C extends self::D implements self::E /*isEliminatedMixin*/  {
   synthetic constructor •() → self::C*
     : super self::D::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.outline.expect
index 6a28c0dd540..e2cba6be4d1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method main() → dynamic
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.expect
index 17fdfdc90db..d2f6483f093 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.transformed.expect
index 17fdfdc90db..d2f6483f093 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.expect
index 17fdfdc90db..d2f6483f093 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.transformed.expect
index 17fdfdc90db..d2f6483f093 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/minimum_int.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.outline.expect
index 4436b0df6bb..a50e142a940 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.outline.expect
@@ -22,7 +22,7 @@ class M extends core::Object {
   synthetic constructor •() → self::M*
     ;
 }
-abstract class _MixinApplication&Super&M = self::Super with self::M {
+abstract class _MixinApplication&Super&M = self::Super with self::M /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.expect
index 4e7c4528f55..b8ba75b43be 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M = self::Super with self::M {
+abstract class _MixinApplication&Super&M = self::Super with self::M /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.transformed.expect
index 4c0f475bf74..f7f4881fbbe 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.strong.transformed.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M extends self::Super implements self::M {
+abstract class _MixinApplication&Super&M extends self::Super implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.expect
index 4e7c4528f55..b8ba75b43be 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M = self::Super with self::M {
+abstract class _MixinApplication&Super&M = self::Super with self::M /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.transformed.expect
index 4c0f475bf74..f7f4881fbbe 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/missing_constructor.dart.weak.transformed.expect
@@ -63,7 +63,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _MixinApplication&Super&M extends self::Super implements self::M {
+abstract class _MixinApplication&Super&M extends self::Super implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor _() → self::_MixinApplication&Super&M*
     : super self::Super::_()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.outline.expect
index a53c688a3f4..9a57e2960b1 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.outline.expect
@@ -2,12 +2,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 = core::Object with self::M1 {
+abstract class _B&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 {
+abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -28,12 +28,12 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     ;
 }
-abstract class _C&Object&M1 = core::Object with self::M1 {
+abstract class _C&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 {
+abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -48,7 +48,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     ;
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.expect
index 4873d85b11c..2cca9cf0caf 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.expect
@@ -2,12 +2,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 = core::Object with self::M1 {
+abstract class _B&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 {
+abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -31,12 +31,12 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 = core::Object with self::M1 {
+abstract class _C&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 {
+abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -53,7 +53,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.transformed.expect
index b36e425650d..b51ef02e7d2 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.strong.transformed.expect
@@ -2,14 +2,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 extends core::Object implements self::M1 {
+abstract class _B&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 {
+abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -35,14 +35,14 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 extends core::Object implements self::M1 {
+abstract class _C&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 {
+abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -61,7 +61,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.expect
index 4873d85b11c..2cca9cf0caf 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.expect
@@ -2,12 +2,12 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 = core::Object with self::M1 {
+abstract class _B&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 {
+abstract class _B&Object&M1&M2 = self::_B&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -31,12 +31,12 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 = core::Object with self::M1 {
+abstract class _C&Object&M1 = core::Object with self::M1 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 {
+abstract class _C&Object&M1&M2 = self::_C&Object&M1 with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -53,7 +53,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> = core::Object with self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.transformed.expect
index b36e425650d..b51ef02e7d2 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin.dart.weak.transformed.expect
@@ -2,14 +2,14 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _B&Object&M1 extends core::Object implements self::M1 {
+abstract class _B&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 {
+abstract class _B&Object&M1&M2 extends self::_B&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M1&M2*
     : super self::_B&Object&M1::•()
     ;
@@ -35,14 +35,14 @@ abstract class M2 extends core::Object {
   method m() → dynamic
     return core::print("M2");
 }
-abstract class _C&Object&M1 extends core::Object implements self::M1 {
+abstract class _C&Object&M1 extends core::Object implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1*
     : super core::Object::•()
     ;
   method m() → dynamic
     return core::print("M1");
 }
-abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 {
+abstract class _C&Object&M1&M2 extends self::_C&Object&M1 implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&M1&M2*
     : super self::_C&Object&M1::•()
     ;
@@ -61,7 +61,7 @@ abstract class G1<T extends core::Object* = dynamic> extends core::Object {
   method m() → dynamic
     return core::print(self::G1::T*);
 }
-abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> {
+abstract class _D&Object&G1<S extends core::Object* = dynamic> extends core::Object implements self::G1<self::_D&Object&G1::S*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_D&Object&G1<self::_D&Object&G1::S*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
index e797e4f595f..b80758f72dc 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class Super extends core::Object {
     : self::Super::field = field, super core::Object::•()
     ;
 }
-class Class extends self::Super implements self::Mixin {
+class Class extends self::Super implements self::Mixin /*isEliminatedMixin*/  {
   synthetic constructor •(core::int* field) → self::Class*
     : super self::Super::•(field)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.weak.transformed.expect
index e797e4f595f..b80758f72dc 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_inferred_parameter_type.dart.weak.transformed.expect
@@ -20,7 +20,7 @@ class Super extends core::Object {
     : self::Super::field = field, super core::Object::•()
     ;
 }
-class Class extends self::Super implements self::Mixin {
+class Class extends self::Super implements self::Mixin /*isEliminatedMixin*/  {
   synthetic constructor •(core::int* field) → self::Class*
     : super self::Super::•(field)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.outline.expect
index 07db82c0c96..50c040ae7d7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.outline.expect
@@ -155,7 +155,7 @@ class A0 = self::S with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A1&S&M1 = self::S with self::M1 {
+abstract class _A1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1&S&M1*
     : super self::S::•()
     ;
@@ -166,12 +166,12 @@ class A1 = self::_A1&S&M1 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A2&S&M1 = self::S with self::M1 {
+abstract class _A2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 {
+abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1&M2*
     : super self::_A2&S&M1::•()
     ;
@@ -182,7 +182,7 @@ class A2 = self::_A2&S&M1&M2 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _A0X&S&M = self::S with self::M {
+abstract class _A0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A0X&S&M*
     : super self::S::•()
     ;
@@ -193,12 +193,12 @@ class A0X = self::_A0X&S&M with self::MX {
     : super self::_A0X&S&M::•()
     ;
 }
-abstract class _A1X&S&M1 = self::S with self::M1 {
+abstract class _A1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M {
+abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1&M*
     : super self::_A1X&S&M1::•()
     ;
@@ -209,17 +209,17 @@ class A1X = self::_A1X&S&M1&M with self::MX {
     : super self::_A1X&S&M1&M::•()
     ;
 }
-abstract class _A2X&S&M1 = self::S with self::M1 {
+abstract class _A2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 {
+abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2*
     : super self::_A2X&S&M1::•()
     ;
 }
-abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M {
+abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2&M*
     : super self::_A2X&S&M1&M2::•()
     ;
@@ -230,7 +230,7 @@ class A2X = self::_A2X&S&M1&M2&M with self::MX {
     : super self::_A2X&S&M1&M2&M::•()
     ;
 }
-abstract class _B0&S&M = self::S with self::M {
+abstract class _B0&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0&S&M*
     : super self::S::•()
     ;
@@ -240,12 +240,12 @@ class B0 extends self::_B0&S&M {
   synthetic constructor •() → self::B0*
     ;
 }
-abstract class _B1&S&M1 = self::S with self::M1 {
+abstract class _B1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M {
+abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1&M*
     : super self::_B1&S&M1::•()
     ;
@@ -255,17 +255,17 @@ class B1 extends self::_B1&S&M1&M {
   synthetic constructor •() → self::B1*
     ;
 }
-abstract class _B2&S&M1 = self::S with self::M1 {
+abstract class _B2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 {
+abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2*
     : super self::_B2&S&M1::•()
     ;
 }
-abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M {
+abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2&M*
     : super self::_B2&S&M1&M2::•()
     ;
@@ -275,13 +275,13 @@ class B2 extends self::_B2&S&M1&M2&M {
   synthetic constructor •() → self::B2*
     ;
 }
-abstract class _B0X&S&M = self::S with self::M {
+abstract class _B0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M*
     : super self::S::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX {
+abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M&MX*
     : super self::_B0X&S&M::•()
     ;
@@ -290,18 +290,18 @@ class B0X extends self::_B0X&S&M&MX {
   synthetic constructor •() → self::B0X*
     ;
 }
-abstract class _B1X&S&M1 = self::S with self::M1 {
+abstract class _B1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M {
+abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M*
     : super self::_B1X&S&M1::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX {
+abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M&MX*
     : super self::_B1X&S&M1&M::•()
     ;
@@ -310,23 +310,23 @@ class B1X extends self::_B1X&S&M1&M&MX {
   synthetic constructor •() → self::B1X*
     ;
 }
-abstract class _B2X&S&M1 = self::S with self::M1 {
+abstract class _B2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 {
+abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2*
     : super self::_B2X&S&M1::•()
     ;
 }
-abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M {
+abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M*
     : super self::_B2X&S&M1&M2::•()
     ;
   abstract forwarding-stub method foo([dynamic x]) → dynamic;
 }
-abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX {
+abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M&MX*
     : super self::_B2X&S&M1&M2&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.strong.expect
index 0fbf4b0ca8d..5ccca350c2b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.strong.expect
@@ -158,7 +158,7 @@ class A0 = self::S with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A1&S&M1 = self::S with self::M1 {
+abstract class _A1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1&S&M1*
     : super self::S::•()
     ;
@@ -169,12 +169,12 @@ class A1 = self::_A1&S&M1 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A2&S&M1 = self::S with self::M1 {
+abstract class _A2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 {
+abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1&M2*
     : super self::_A2&S&M1::•()
     ;
@@ -185,7 +185,7 @@ class A2 = self::_A2&S&M1&M2 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A0X&S&M = self::S with self::M {
+abstract class _A0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A0X&S&M*
     : super self::S::•()
     ;
@@ -196,12 +196,12 @@ class A0X = self::_A0X&S&M with self::MX {
     : super self::_A0X&S&M::•()
     ;
 }
-abstract class _A1X&S&M1 = self::S with self::M1 {
+abstract class _A1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M {
+abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1&M*
     : super self::_A1X&S&M1::•()
     ;
@@ -212,17 +212,17 @@ class A1X = self::_A1X&S&M1&M with self::MX {
     : super self::_A1X&S&M1&M::•()
     ;
 }
-abstract class _A2X&S&M1 = self::S with self::M1 {
+abstract class _A2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 {
+abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2*
     : super self::_A2X&S&M1::•()
     ;
 }
-abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M {
+abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2&M*
     : super self::_A2X&S&M1&M2::•()
     ;
@@ -233,7 +233,7 @@ class A2X = self::_A2X&S&M1&M2&M with self::MX {
     : super self::_A2X&S&M1&M2&M::•()
     ;
 }
-abstract class _B0&S&M = self::S with self::M {
+abstract class _B0&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0&S&M*
     : super self::S::•()
     ;
@@ -244,12 +244,12 @@ class B0 extends self::_B0&S&M {
     : super self::_B0&S&M::•()
     ;
 }
-abstract class _B1&S&M1 = self::S with self::M1 {
+abstract class _B1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M {
+abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1&M*
     : super self::_B1&S&M1::•()
     ;
@@ -260,17 +260,17 @@ class B1 extends self::_B1&S&M1&M {
     : super self::_B1&S&M1&M::•()
     ;
 }
-abstract class _B2&S&M1 = self::S with self::M1 {
+abstract class _B2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 {
+abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2*
     : super self::_B2&S&M1::•()
     ;
 }
-abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M {
+abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2&M*
     : super self::_B2&S&M1&M2::•()
     ;
@@ -281,13 +281,13 @@ class B2 extends self::_B2&S&M1&M2&M {
     : super self::_B2&S&M1&M2&M::•()
     ;
 }
-abstract class _B0X&S&M = self::S with self::M {
+abstract class _B0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M*
     : super self::S::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX {
+abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M&MX*
     : super self::_B0X&S&M::•()
     ;
@@ -297,18 +297,18 @@ class B0X extends self::_B0X&S&M&MX {
     : super self::_B0X&S&M&MX::•()
     ;
 }
-abstract class _B1X&S&M1 = self::S with self::M1 {
+abstract class _B1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M {
+abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M*
     : super self::_B1X&S&M1::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX {
+abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M&MX*
     : super self::_B1X&S&M1&M::•()
     ;
@@ -318,23 +318,23 @@ class B1X extends self::_B1X&S&M1&M&MX {
     : super self::_B1X&S&M1&M&MX::•()
     ;
 }
-abstract class _B2X&S&M1 = self::S with self::M1 {
+abstract class _B2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 {
+abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2*
     : super self::_B2X&S&M1::•()
     ;
 }
-abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M {
+abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M*
     : super self::_B2X&S&M1&M2::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX {
+abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M&MX*
     : super self::_B2X&S&M1&M2&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.weak.expect
index 0fbf4b0ca8d..5ccca350c2b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_application_override.dart.weak.expect
@@ -158,7 +158,7 @@ class A0 = self::S with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A1&S&M1 = self::S with self::M1 {
+abstract class _A1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1&S&M1*
     : super self::S::•()
     ;
@@ -169,12 +169,12 @@ class A1 = self::_A1&S&M1 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A2&S&M1 = self::S with self::M1 {
+abstract class _A2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 {
+abstract class _A2&S&M1&M2 = self::_A2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2&S&M1&M2*
     : super self::_A2&S&M1::•()
     ;
@@ -185,7 +185,7 @@ class A2 = self::_A2&S&M1&M2 with self::M {
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _A0X&S&M = self::S with self::M {
+abstract class _A0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A0X&S&M*
     : super self::S::•()
     ;
@@ -196,12 +196,12 @@ class A0X = self::_A0X&S&M with self::MX {
     : super self::_A0X&S&M::•()
     ;
 }
-abstract class _A1X&S&M1 = self::S with self::M1 {
+abstract class _A1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M {
+abstract class _A1X&S&M1&M = self::_A1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A1X&S&M1&M*
     : super self::_A1X&S&M1::•()
     ;
@@ -212,17 +212,17 @@ class A1X = self::_A1X&S&M1&M with self::MX {
     : super self::_A1X&S&M1&M::•()
     ;
 }
-abstract class _A2X&S&M1 = self::S with self::M1 {
+abstract class _A2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 {
+abstract class _A2X&S&M1&M2 = self::_A2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2*
     : super self::_A2X&S&M1::•()
     ;
 }
-abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M {
+abstract class _A2X&S&M1&M2&M = self::_A2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A2X&S&M1&M2&M*
     : super self::_A2X&S&M1&M2::•()
     ;
@@ -233,7 +233,7 @@ class A2X = self::_A2X&S&M1&M2&M with self::MX {
     : super self::_A2X&S&M1&M2&M::•()
     ;
 }
-abstract class _B0&S&M = self::S with self::M {
+abstract class _B0&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0&S&M*
     : super self::S::•()
     ;
@@ -244,12 +244,12 @@ class B0 extends self::_B0&S&M {
     : super self::_B0&S&M::•()
     ;
 }
-abstract class _B1&S&M1 = self::S with self::M1 {
+abstract class _B1&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M {
+abstract class _B1&S&M1&M = self::_B1&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1&S&M1&M*
     : super self::_B1&S&M1::•()
     ;
@@ -260,17 +260,17 @@ class B1 extends self::_B1&S&M1&M {
     : super self::_B1&S&M1&M::•()
     ;
 }
-abstract class _B2&S&M1 = self::S with self::M1 {
+abstract class _B2&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 {
+abstract class _B2&S&M1&M2 = self::_B2&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2*
     : super self::_B2&S&M1::•()
     ;
 }
-abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M {
+abstract class _B2&S&M1&M2&M = self::_B2&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2&S&M1&M2&M*
     : super self::_B2&S&M1&M2::•()
     ;
@@ -281,13 +281,13 @@ class B2 extends self::_B2&S&M1&M2&M {
     : super self::_B2&S&M1&M2&M::•()
     ;
 }
-abstract class _B0X&S&M = self::S with self::M {
+abstract class _B0X&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M*
     : super self::S::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX {
+abstract class _B0X&S&M&MX = self::_B0X&S&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B0X&S&M&MX*
     : super self::_B0X&S&M::•()
     ;
@@ -297,18 +297,18 @@ class B0X extends self::_B0X&S&M&MX {
     : super self::_B0X&S&M&MX::•()
     ;
 }
-abstract class _B1X&S&M1 = self::S with self::M1 {
+abstract class _B1X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M {
+abstract class _B1X&S&M1&M = self::_B1X&S&M1 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M*
     : super self::_B1X&S&M1::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX {
+abstract class _B1X&S&M1&M&MX = self::_B1X&S&M1&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B1X&S&M1&M&MX*
     : super self::_B1X&S&M1&M::•()
     ;
@@ -318,23 +318,23 @@ class B1X extends self::_B1X&S&M1&M&MX {
     : super self::_B1X&S&M1&M&MX::•()
     ;
 }
-abstract class _B2X&S&M1 = self::S with self::M1 {
+abstract class _B2X&S&M1 = self::S with self::M1 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1*
     : super self::S::•()
     ;
 }
-abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 {
+abstract class _B2X&S&M1&M2 = self::_B2X&S&M1 with self::M2 /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2*
     : super self::_B2X&S&M1::•()
     ;
 }
-abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M {
+abstract class _B2X&S&M1&M2&M = self::_B2X&S&M1&M2 with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M*
     : super self::_B2X&S&M1&M2::•()
     ;
   abstract forwarding-stub method foo([dynamic x = #C1]) → dynamic;
 }
-abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX {
+abstract class _B2X&S&M1&M2&M&MX = self::_B2X&S&M1&M2&M with self::MX /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_B2X&S&M1&M2&M&MX*
     : super self::_B2X&S&M1&M2&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.outline.expect
index 8ecf33b7e34..67867e333a9 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.outline.expect
@@ -44,7 +44,7 @@ class N = core::Object with self::M {
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&N = core::Object with self::N {
+abstract class _C&Object&N = core::Object with self::N /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -69,7 +69,7 @@ abstract class N3 = core::Object with self::M2 {
     : super core::Object::•()
     ;
 }
-abstract class _C2&Object&M2 = core::Object with self::M2 {
+abstract class _C2&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -78,7 +78,7 @@ class C2 extends self::_C2&Object&M2 {
   synthetic constructor •() → self::C2*
     ;
 }
-abstract class _C3&Object&M2 = core::Object with self::M2 {
+abstract class _C3&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.expect
index c8ffe22ee3e..7f6f63dc9d8 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.expect
@@ -44,7 +44,7 @@ class N = core::Object with self::M {
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&N = core::Object with self::N {
+abstract class _C&Object&N = core::Object with self::N /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -70,7 +70,7 @@ abstract class N3 = core::Object with self::M2 {
     : super core::Object::•()
     ;
 }
-abstract class _C2&Object&M2 = core::Object with self::M2 {
+abstract class _C2&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -80,7 +80,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 = core::Object with self::M2 {
+abstract class _C3&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.transformed.expect
index b81769ab0fd..964368fb38b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.strong.transformed.expect
@@ -39,13 +39,13 @@ class M extends core::Object {
     ;
   method foo() → dynamic {}
 }
-class N extends core::Object implements self::M {
+class N extends core::Object implements self::M /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N*
     : super core::Object::•()
     ;
   method foo() → dynamic {}
 }
-abstract class _C&Object&N extends core::Object implements self::N {
+abstract class _C&Object&N extends core::Object implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -62,19 +62,19 @@ abstract class M2 extends core::Object implements self::M {
     ;
   method bar() → dynamic {}
 }
-class N2 extends core::Object implements self::M2 {
+class N2 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N2*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class N3 extends core::Object implements self::M2 {
+abstract class N3 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N3*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class _C2&Object&M2 extends core::Object implements self::M2 {
+abstract class _C2&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -85,7 +85,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 extends core::Object implements self::M2 {
+abstract class _C3&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.expect
index c8ffe22ee3e..7f6f63dc9d8 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.expect
@@ -44,7 +44,7 @@ class N = core::Object with self::M {
     : super core::Object::•()
     ;
 }
-abstract class _C&Object&N = core::Object with self::N {
+abstract class _C&Object&N = core::Object with self::N /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -70,7 +70,7 @@ abstract class N3 = core::Object with self::M2 {
     : super core::Object::•()
     ;
 }
-abstract class _C2&Object&M2 = core::Object with self::M2 {
+abstract class _C2&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -80,7 +80,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 = core::Object with self::M2 {
+abstract class _C3&Object&M2 = core::Object with self::M2 /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.transformed.expect
index b81769ab0fd..964368fb38b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_conflicts.dart.weak.transformed.expect
@@ -39,13 +39,13 @@ class M extends core::Object {
     ;
   method foo() → dynamic {}
 }
-class N extends core::Object implements self::M {
+class N extends core::Object implements self::M /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N*
     : super core::Object::•()
     ;
   method foo() → dynamic {}
 }
-abstract class _C&Object&N extends core::Object implements self::N {
+abstract class _C&Object&N extends core::Object implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&N*
     : super core::Object::•()
     ;
@@ -62,19 +62,19 @@ abstract class M2 extends core::Object implements self::M {
     ;
   method bar() → dynamic {}
 }
-class N2 extends core::Object implements self::M2 {
+class N2 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N2*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class N3 extends core::Object implements self::M2 {
+abstract class N3 extends core::Object implements self::M2 /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::N3*
     : super core::Object::•()
     ;
   method bar() → dynamic {}
 }
-abstract class _C2&Object&M2 extends core::Object implements self::M2 {
+abstract class _C2&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C2&Object&M2*
     : super core::Object::•()
     ;
@@ -85,7 +85,7 @@ class C2 extends self::_C2&Object&M2 {
     : super self::_C2&Object&M2::•()
     ;
 }
-abstract class _C3&Object&M2 extends core::Object implements self::M2 {
+abstract class _C3&Object&M2 extends core::Object implements self::M2 /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C3&Object&M2*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.outline.expect
index 7c8f4ee13a1..9c0a4edfa85 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.outline.expect
@@ -22,7 +22,7 @@ class E extends self::D {
   synthetic constructor •() → self::E*
     ;
 }
-abstract class _F&C&M = self::C<core::int*> with self::M {
+abstract class _F&C&M = self::C<core::int*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •({dynamic a, dynamic b}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.expect
index 66b645612d6..500a9d3aa1b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.expect
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M = self::C<core::int*> with self::M {
+abstract class _F&C&M = self::C<core::int*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.transformed.expect
index da125056bec..9c19e86ea67 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.strong.transformed.expect
@@ -29,7 +29,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class D extends self::C<core::String*> implements self::M {
+class D extends self::C<core::String*> implements self::M /*isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C2}) → self::D*
     : super self::C::•(a: a, b: b)
     ;
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M extends self::C<core::int*> implements self::M {
+abstract class _F&C&M extends self::C<core::int*> implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.expect
index 66b645612d6..500a9d3aa1b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.expect
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M = self::C<core::int*> with self::M {
+abstract class _F&C&M = self::C<core::int*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.transformed.expect
index da125056bec..9c19e86ea67 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_constructors_with_default_values.dart.weak.transformed.expect
@@ -29,7 +29,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class D extends self::C<core::String*> implements self::M {
+class D extends self::C<core::String*> implements self::M /*isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C2}) → self::D*
     : super self::C::•(a: a, b: b)
     ;
@@ -39,7 +39,7 @@ class E extends self::D {
     : super self::D::•()
     ;
 }
-abstract class _F&C&M extends self::C<core::int*> implements self::M {
+abstract class _F&C&M extends self::C<core::int*> implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •({dynamic a = #C1, dynamic b = #C3}) → self::_F&C&M*
     : super self::C::•(a: a, b: b)
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
index 5d6839715e7..3b41508ff8d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.outline.expect
@@ -17,7 +17,7 @@ class D extends self::C<self::B*> {
   synthetic constructor •() → self::D*
     ;
 }
-abstract class _Foo&Object&C = core::Object with self::C<self::B*> {
+abstract class _Foo&Object&C = core::Object with self::C<self::B*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
index 9081947fb10..467b3b598ba 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C = core::Object with self::C<self::B*> {
+abstract class _Foo&Object&C = core::Object with self::C<self::B*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
index 8d9258937c7..6b9150f933c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.strong.transformed.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> {
+abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> /*isAnonymousMixin,isEliminatedMixin*/  {
   generic-covariant-impl field self::B* _field = null;
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.expect
index 9081947fb10..467b3b598ba 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C = core::Object with self::C<self::B*> {
+abstract class _Foo&Object&C = core::Object with self::C<self::B*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.transformed.expect
index 8d9258937c7..6b9150f933c 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_inherited_setter_for_mixed_in_field.dart.weak.transformed.expect
@@ -21,7 +21,7 @@ class D extends self::C<self::B*> {
     : super self::C::•()
     ;
 }
-abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> {
+abstract class _Foo&Object&C extends core::Object implements self::C<self::B*> /*isAnonymousMixin,isEliminatedMixin*/  {
   generic-covariant-impl field self::B* _field = null;
   synthetic constructor •() → self::_Foo&Object&C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.outline.expect
index 7e6110bd9eb..13e9d2562b8 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.outline.expect
@@ -19,12 +19,12 @@ class S extends core::Object {
   synthetic constructor •() → self::S*
     ;
 }
-abstract class _Named&S&M = self::S with self::M {
+abstract class _Named&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N = self::_Named&S&M with self::N {
+abstract class _Named&S&M&N = self::_Named&S&M with self::N /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.expect
index 1dc80512eb5..085e258a30e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.expect
@@ -23,12 +23,12 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M = self::S with self::M {
+abstract class _Named&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N = self::_Named&S&M with self::N {
+abstract class _Named&S&M&N = self::_Named&S&M with self::N /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.transformed.expect
index 14cb42dd3f8..ad780133565 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.strong.transformed.expect
@@ -23,13 +23,13 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M extends self::S implements self::M {
+abstract class _Named&S&M extends self::S implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
+abstract class _Named&S&M&N extends self::_Named&S&M implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
@@ -39,7 +39,7 @@ abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
   get superM() → dynamic
     return super.{self::M::m};
 }
-class Named extends self::_Named&S&M&N implements self::M {
+class Named extends self::_Named&S&M&N implements self::M /*isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::Named*
     : super self::_Named&S&M&N::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.expect
index 1dc80512eb5..085e258a30e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.expect
@@ -23,12 +23,12 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M = self::S with self::M {
+abstract class _Named&S&M = self::S with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N = self::_Named&S&M with self::N {
+abstract class _Named&S&M&N = self::_Named&S&M with self::N /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.transformed.expect
index 14cb42dd3f8..ad780133565 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_super_repeated.dart.weak.transformed.expect
@@ -23,13 +23,13 @@ class S extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Named&S&M extends self::S implements self::M {
+abstract class _Named&S&M extends self::S implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::_Named&S&M*
     : super self::S::•()
     ;
 }
-abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
+abstract class _Named&S&M&N extends self::_Named&S&M implements self::N /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Named&S&M&N*
     : super self::_Named&S&M::•()
     ;
@@ -39,7 +39,7 @@ abstract class _Named&S&M&N extends self::_Named&S&M implements self::N {
   get superM() → dynamic
     return super.{self::M::m};
 }
-class Named extends self::_Named&S&M&N implements self::M {
+class Named extends self::_Named&S&M&N implements self::M /*isEliminatedMixin*/  {
   field dynamic m = null;
   synthetic constructor •() → self::Named*
     : super self::_Named&S&M&N::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.outline.expect
index c82f01d24e0..f982247c68d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M = self::B with self::M {
+abstract class _A&B&M = self::B with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.expect
index a6968d34727..85e498d6a9d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M = self::B with self::M {
+abstract class _A&B&M = self::B with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.transformed.expect
index a7328585c77..b9faaa3b7cc 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M extends self::B implements self::M {
+abstract class _A&B&M extends self::B implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.expect
index a6968d34727..85e498d6a9d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M = self::B with self::M {
+abstract class _A&B&M = self::B with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.transformed.expect
index a7328585c77..b9faaa3b7cc 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/mixin_with_static_member.dart.weak.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class _A&B&M extends self::B implements self::M {
+abstract class _A&B&M extends self::B implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&B&M*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.outline.expect
index 536cae19a94..f42f11fb9b4 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.outline.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.transformed.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.strong.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.transformed.expect
index 6a1ea6dc847..ec1126cd7cd 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/nested_implicit_const_with_env_var.dart.weak.transformed.expect
@@ -2,13 +2,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* bar;
   const constructor •(core::int* bar) → self::A*
     : self::A::bar = bar, super core::Object::•()
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   final field self::A* baz;
   const constructor •(self::A* baz) → self::B*
     : self::B::baz = baz, super core::Object::•()
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.outline.expect
index 2c007ed12a3..5d86d97f5d5 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.outline.expect
@@ -34,7 +34,7 @@ class Bad extends core::Object {
   static factory WrongName() → self::Bad*
     ;
 }
-abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.expect
index ea0d1455dea..466b5c297ce 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.transformed.expect
index 0ae01e93ccb..82668652f5d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.strong.transformed.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.expect
index ea0d1455dea..466b5c297ce 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin = lib::Supertype with lib::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.transformed.expect
index 0ae01e93ccb..82668652f5d 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/qualified.dart.weak.transformed.expect
@@ -32,7 +32,7 @@ class Bad extends core::Object {
   method method() → invalid-type {}
   static factory WrongName() → self::Bad* {}
 }
-abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin {
+abstract class _WithMixin&Supertype&Mixin extends lib::Supertype implements lib::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_WithMixin&Supertype&Mixin*
     : super lib::Supertype::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.strong.transformed.expect
index 0b5a926776c..c2e98d0de7e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.strong.transformed.expect
@@ -62,7 +62,7 @@ class Mixin<M extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> {
+class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Mix<self::Mix::M*>*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.weak.transformed.expect
index 0b5a926776c..c2e98d0de7e 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory.dart.weak.transformed.expect
@@ -62,7 +62,7 @@ class Mixin<M extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> {
+class Mix<M extends core::Object* = dynamic> extends self::Base<self::Mix::M*> implements self::Mixin<self::Mix::M*> /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Mix<self::Mix::M*>*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.outline.expect
index 2d1371090af..3ed80bfd485 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.outline.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let dynamic #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.expect
index 87fc76e26c2..397a76d1c9b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let dynamic #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.transformed.expect
index 03943113373..2b04ded0b1a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.strong.transformed.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let<BottomType> #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.expect
index 87fc76e26c2..397a76d1c9b 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let dynamic #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.transformed.expect
index 03943113373..2b04ded0b1a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirecting_factory_const_inference.dart.weak.transformed.expect
@@ -7,7 +7,7 @@ class _X<T extends core::Object* = dynamic> extends core::Object {
   static factory •<T extends core::Object* = dynamic>() → self::_X<self::_X::•::T*>*
     let<BottomType> #redirecting_factory = self::_Y::• in let self::_X::•::T* #typeArg0 = null in invalid-expression;
 }
-class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> {
+class _Y<T extends core::Object* = dynamic> extends core::Object implements self::_X<self::_Y::T*> /*hasConstConstructor*/  {
   const constructor •() → self::_Y<self::_Y::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.outline.expect
index 41181941707..b15ac8d6d7a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.outline.expect
@@ -4,7 +4,7 @@ import "dart:core" as core;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -12,7 +12,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let dynamic #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.expect
index a87fba5fcdb..81c22f9b7e7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let dynamic #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.transformed.expect
index d6f34c92c48..8c2291db438 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.strong.transformed.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let<BottomType> #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.expect
index a87fba5fcdb..81c22f9b7e7 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let dynamic #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.transformed.expect
index d6f34c92c48..8c2291db438 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/redirection_type_arguments.dart.weak.transformed.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::A::•];
   const constructor empty() → self::A*
     : super core::Object::•()
@@ -13,7 +13,7 @@ class A extends core::Object {
   static factory •() → self::A*
     let<BottomType> #redirecting_factory = self::B::• in let core::String* #typeArg0 = null in invalid-expression;
 }
-class B<T extends core::Object* = dynamic> extends self::A {
+class B<T extends core::Object* = dynamic> extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::T*>*
     : super self::A::empty()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.outline.expect
index 253f7312ee2..c570402d61f 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.outline.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.expect
index 0f110873f9f..3c479e01f6a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.transformed.expect
index 0f110873f9f..3c479e01f6a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.strong.transformed.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.expect
index 0f110873f9f..3c479e01f6a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.transformed.expect
index 0f110873f9f..3c479e01f6a 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_literal_as_metadata.dart.weak.transformed.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.outline.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.outline.expect
index de5a4aaaf86..d05b2f546a6 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.outline.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.outline.expect
@@ -9,7 +9,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.expect
index 1b3c50ceb75..3d8ba364857 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.transformed.expect
index 1b3c50ceb75..3d8ba364857 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.strong.transformed.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.expect
index 1b3c50ceb75..3d8ba364857 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.transformed.expect
index 1b3c50ceb75..3d8ba364857 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/type_variable_uses.dart.weak.transformed.expect
@@ -65,7 +65,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.1.expect
index 5dfc563500a..acc9d659da0 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.1.expect
@@ -23,7 +23,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
       ;
     method hello(covariant lib::FooEntry* entry) → void {}
   }
-  abstract class MyMixin extends lib::Baz {
+  abstract class MyMixin extends lib::Baz /*isMixinDeclaration*/  {
   }
   abstract class Qux extends lib::Baz {
     synthetic constructor •() → lib::Qux*
@@ -31,7 +31,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
       ;
     method hello(covariant lib::BarEntry* entry) → void {}
   }
-  abstract class _Quux&Qux&MyMixin extends lib::Qux implements lib::MyMixin {
+  abstract class _Quux&Qux&MyMixin extends lib::Qux implements lib::MyMixin /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → lib::_Quux&Qux&MyMixin*
       : super lib::Qux::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.2.expect
index f0b2d5e9556..c05c80156e6 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/flutter_mixin_failure_1.yaml.world.2.expect
@@ -23,7 +23,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
       ;
     method hello(covariant lib::FooEntry* entry) → void {}
   }
-  abstract class MyMixin extends lib::Baz {
+  abstract class MyMixin extends lib::Baz /*isMixinDeclaration*/  {
   }
   abstract class Qux extends lib::Baz {
     synthetic constructor •() → lib::Qux*
@@ -31,7 +31,7 @@ library from "org-dartlang-test:///lib.dart" as lib {
       ;
     method hello(covariant lib::BarEntry* entry) → void {}
   }
-  abstract class _Quux&Qux&MyMixin extends lib::Qux implements lib::MyMixin {
+  abstract class _Quux&Qux&MyMixin extends lib::Qux implements lib::MyMixin /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → lib::_Quux&Qux&MyMixin*
       : super lib::Qux::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/mixin_inferrer_error.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/mixin_inferrer_error.yaml.world.1.expect
index b2daf411c05..1c539141ac5 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/mixin_inferrer_error.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/mixin_inferrer_error.yaml.world.1.expect
@@ -21,9 +21,9 @@ library from "org-dartlang-test:///main.dart" as main {
       : super dart.core::Object::•()
       ;
   }
-  abstract class M<T extends dart.core::Object* = dynamic> extends main::A<main::M::T*> {
+  abstract class M<T extends dart.core::Object* = dynamic> extends main::A<main::M::T*> /*isMixinDeclaration*/  {
   }
-  abstract class _C&Object&M extends dart.core::Object implements main::M<dynamic> {
+  abstract class _C&Object&M extends dart.core::Object implements main::M<dynamic> /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → main::_C&Object&M*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_13.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_13.yaml.world.1.expect
index 90ad9291791..ca91b00d3b6 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_13.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_13.yaml.world.1.expect
@@ -8,7 +8,7 @@ additionalExports = (lib2::Foo)
 }
 library from "org-dartlang-test:///lib2.dart" as lib2 {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     static const field lib2::Foo* BAR = #C1;
     const constructor •(dart.core::String* x) → lib2::Foo*
       : super dart.core::Object::•()
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_2.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_2.yaml.world.1.expect
index 761708e4da4..321e0eb3352 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_2.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_2.yaml.world.1.expect
@@ -21,7 +21,7 @@ library from "org-dartlang-test:///main.dart" as main {
       return "${this.{main::Foo::message}}";
     }
   }
-  class CompilationStrategy extends dart.core::Object {
+  class CompilationStrategy extends dart.core::Object /*isEnum*/  {
     final field dart.core::int* index;
     final field dart.core::String* _name;
     static const field dart.core::List<main::CompilationStrategy*>* values = #C14;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.1.expect
index faa6a66ecb9..b9ec6ce4ede 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.1.expect
@@ -3,7 +3,7 @@ library from "org-dartlang-test:///main.dart" as main {
 
   import "dart:collection";
 
-  abstract class _WithListMixin&Object&ListMixin extends dart.core::Object implements dart.collection::ListMixin<dart.core::int*> {
+  abstract class _WithListMixin&Object&ListMixin extends dart.core::Object implements dart.collection::ListMixin<dart.core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → main::_WithListMixin&Object&ListMixin*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.2.expect
index faa6a66ecb9..b9ec6ce4ede 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_22.yaml.world.2.expect
@@ -3,7 +3,7 @@ library from "org-dartlang-test:///main.dart" as main {
 
   import "dart:collection";
 
-  abstract class _WithListMixin&Object&ListMixin extends dart.core::Object implements dart.collection::ListMixin<dart.core::int*> {
+  abstract class _WithListMixin&Object&ListMixin extends dart.core::Object implements dart.collection::ListMixin<dart.core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → main::_WithListMixin&Object&ListMixin*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.1.expect
index dc036f00685..f4a1dddc108 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.1.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///main.dart" as main {
 
-  abstract class _A&Object&B extends dart.core::Object implements main::B {
+  abstract class _A&Object&B extends dart.core::Object implements main::B /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → main::_A&Object&B*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.2.expect
index dc036f00685..f4a1dddc108 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_23.yaml.world.2.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///main.dart" as main {
 
-  abstract class _A&Object&B extends dart.core::Object implements main::B {
+  abstract class _A&Object&B extends dart.core::Object implements main::B /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → main::_A&Object&B*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.1.expect
index 74a7dbe8381..7bc33641b68 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.1.expect
@@ -9,22 +9,22 @@ library from "org-dartlang-test:///main.dart" as main {
       dart.core::print("Class A method a");
     }
   }
-  abstract class B extends main::A {
+  abstract class B extends main::A /*isMixinDeclaration*/  {
     method b() → dynamic {
       dart.core::print("Class A method b");
     }
   }
-  abstract class _C&A&B extends dart.core::Object implements main::A, main::B {
+  abstract class _C&A&B extends dart.core::Object implements main::A, main::B /*isAnonymousMixin*/  {
     synthetic constructor •() → main::_C&A&B*
       : super dart.core::Object::•()
       ;
   }
-  abstract class C extends main::_C&A&B {
+  abstract class C extends main::_C&A&B /*isMixinDeclaration*/  {
     method c() → dynamic {
       dart.core::print("Class C method c");
     }
   }
-  abstract class _D&A&B extends main::A implements main::B {
+  abstract class _D&A&B extends main::A implements main::B /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → main::_D&A&B*
       : super main::A::•()
       ;
@@ -32,7 +32,7 @@ library from "org-dartlang-test:///main.dart" as main {
       dart.core::print("Class A method b");
     }
   }
-  abstract class _D&A&B&C extends main::_D&A&B implements main::C {
+  abstract class _D&A&B&C extends main::_D&A&B implements main::C /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → main::_D&A&B&C*
       : super main::_D&A&B::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.2.expect
index 685e8c404db..e24322218e7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_28.yaml.world.2.expect
@@ -9,22 +9,22 @@ library from "org-dartlang-test:///main.dart" as main {
       dart.core::print("Class A method a!");
     }
   }
-  abstract class B extends main::A {
+  abstract class B extends main::A /*isMixinDeclaration*/  {
     method b() → dynamic {
       dart.core::print("Class A method b!");
     }
   }
-  abstract class _C&A&B extends dart.core::Object implements main::A, main::B {
+  abstract class _C&A&B extends dart.core::Object implements main::A, main::B /*isAnonymousMixin*/  {
     synthetic constructor •() → main::_C&A&B*
       : super dart.core::Object::•()
       ;
   }
-  abstract class C extends main::_C&A&B {
+  abstract class C extends main::_C&A&B /*isMixinDeclaration*/  {
     method c() → dynamic {
       dart.core::print("Class C method c!");
     }
   }
-  abstract class _D&A&B extends main::A implements main::B {
+  abstract class _D&A&B extends main::A implements main::B /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → main::_D&A&B*
       : super main::A::•()
       ;
@@ -32,7 +32,7 @@ library from "org-dartlang-test:///main.dart" as main {
       dart.core::print("Class A method b!");
     }
   }
-  abstract class _D&A&B&C extends main::_D&A&B implements main::C {
+  abstract class _D&A&B&C extends main::_D&A&B implements main::C /*isAnonymousMixin,isEliminatedMixin*/  {
     synthetic constructor •() → main::_D&A&B&C*
       : super main::_D&A&B::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.1.expect
index 91e848702b1..b765c135719 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.1.expect
@@ -36,7 +36,7 @@ library from "org-dartlang-test:///main.dart" as main {
 
   import "org-dartlang-test:///libA.dart";
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → main::Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.2.expect
index b5437cc22d4..c5de17c3ac8 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_3.yaml.world.2.expect
@@ -36,7 +36,7 @@ library from "org-dartlang-test:///main.dart" as main {
 
   import "org-dartlang-test:///libA.dart";
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → main::Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.1.expect
index a2166d94e0e..174ad0423fe 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.1.expect
@@ -3,7 +3,7 @@ library from "org-dartlang-test:///libA.dart" as libA {
 
   import "org-dartlang-test:///main.dart";
 
-  abstract class _Bar&Object&Foo extends dart.core::Object implements main::Foo {
+  abstract class _Bar&Object&Foo extends dart.core::Object implements main::Foo /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → libA::_Bar&Object&Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.2.expect
index 6ec9787e754..089f7dc4629 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_4.yaml.world.2.expect
@@ -3,7 +3,7 @@ library from "org-dartlang-test:///libA.dart" as libA {
 
   import "org-dartlang-test:///main.dart";
 
-  abstract class _Bar&Object&Foo extends dart.core::Object implements main::Foo {
+  abstract class _Bar&Object&Foo extends dart.core::Object implements main::Foo /*isAnonymousMixin,isEliminatedMixin*/  {
     const synthetic constructor •() → libA::_Bar&Object&Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.1.expect
index 164275cc90f..42d71208cb8 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.1.expect
@@ -2,7 +2,7 @@ main = <No Member>;
 library from "org-dartlang-test:///main.dart" as main {
 
   part myPart.dart;
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → main::Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.2.expect
index eda5685d368..418248d0519 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.2.expect
@@ -2,7 +2,7 @@ main = <No Member>;
 library from "org-dartlang-test:///main.dart" as main {
 
   part myPart.dart;
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → main::Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.3.expect
index 488e237d12d..13582f45de7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_5.yaml.world.3.expect
@@ -2,7 +2,7 @@ main = <No Member>;
 library from "org-dartlang-test:///main.dart" as main {
 
   part myPart.dart;
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → main::Foo*
       : super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_6.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_6.yaml.world.1.expect
index db672dba07d..eff9cc35705 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_6.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_6.yaml.world.1.expect
@@ -28,7 +28,7 @@ library from "org-dartlang-test:///main.dart" as main {
       return "${this.{main::Foo::message}}";
     }
   }
-  class CompilationStrategy extends dart.core::Object {
+  class CompilationStrategy extends dart.core::Object /*isEnum*/  {
     final field dart.core::int* index;
     final field dart.core::String* _name;
     static const field dart.core::List<main::CompilationStrategy*>* values = #C14;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_7.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_7.yaml.world.1.expect
index 05b87bbb102..a766d584087 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_7.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/no_outline_change_7.yaml.world.1.expect
@@ -32,7 +32,7 @@ library from "org-dartlang-test:///main.dart" as main {
     }
   }
   @#C1
-  class CompilationStrategy extends dart.core::Object {
+  class CompilationStrategy extends dart.core::Object /*isEnum*/  {
     final field dart.core::int* index;
     final field dart.core::String* _name;
     static const field dart.core::List<main::CompilationStrategy*>* values = #C15;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.1.expect
index e14d84017f1..c34880199f7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.1.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.2.expect
index 775fa518592..330e86a362b 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.2.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.3.expect
index 2a323b6ff97..d94840c04ca 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.3.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.4.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.4.expect
index 5da49818e14..4448e20820b 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.4.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.4.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.5.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.5.expect
index 79519c158f4..0a98dfb98f6 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.5.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_10.yaml.world.5.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.1.expect
index e14d84017f1..c34880199f7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.1.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.2.expect
index ced3bbfeac0..d55ef0b8033 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.2.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
@@ -14,7 +14,7 @@ library from "org-dartlang-test:///lib2.dart" as lib2 {
 
   import "org-dartlang-test:///lib.dart";
 
-  class Bar extends dart.core::Object {
+  class Bar extends dart.core::Object /*hasConstConstructor*/  {
     final field lib::Foo* x;
     const constructor •() → lib2::Bar*
       : lib2::Bar::x = invalid-expression "This assertion failed.", super dart.core::Object::•()
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.3.expect
index b2125955829..ea9b7e748c2 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_11.yaml.world.3.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
@@ -14,7 +14,7 @@ library from "org-dartlang-test:///lib2.dart" as lib2 {
 
   import "org-dartlang-test:///lib.dart";
 
-  class Bar extends dart.core::Object {
+  class Bar extends dart.core::Object /*hasConstConstructor*/  {
     final field lib::Foo* x;
     const constructor •() → lib2::Bar*
       : lib2::Bar::x = #C1, super dart.core::Object::•()
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.1.expect
index e14d84017f1..c34880199f7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.1.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.2.expect
index fd1eaf90231..6beddd64a97 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.2.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.3.expect
index e14d84017f1..c34880199f7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_8.yaml.world.3.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.1.expect
index e14d84017f1..c34880199f7 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.1.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.2.expect
index b96fc855164..ec21fb45cb8 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.2.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.3.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.3.expect
index 06f21af4ce1..f105755c36a 100644
--- a/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.3.expect
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/reissue_errors_9.yaml.world.3.expect
@@ -1,7 +1,7 @@
 main = <No Member>;
 library from "org-dartlang-test:///lib.dart" as lib {
 
-  class Foo extends dart.core::Object {
+  class Foo extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •(dart.core::int* i) → lib::Foo*
       : assert(i.{dart.core::num::>}(0)), super dart.core::Object::•()
       ;
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.outline.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.outline.expect
index da1258fc2db..b4b1520e1fc 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* t;
   const constructor •(self::C::T* t) → self::C<self::C::T*>*
     : self::C::t = t, super core::Object::•()
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.expect
index 6aa1ff0ea44..508226b679b 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* t;
   const constructor •(self::C::T* t) → self::C<self::C::T*>*
     : self::C::t = t, super core::Object::•()
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.transformed.expect
index 6aa1ff0ea44..508226b679b 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* t;
   const constructor •(self::C::T* t) → self::C<self::C::T*>*
     : self::C::t = t, super core::Object::•()
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.outline.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.outline.expect
index cbb70eb9632..8622004bc41 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.outline.expect
@@ -2,13 +2,13 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::num* = core::num*> extends core::Object {
+class C<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* x;
   const constructor •(self::C::T* x) → self::C<self::C::T*>*
     : self::C::x = x, super core::Object::•()
     ;
 }
-class D<T extends core::num* = core::num*> extends core::Object {
+class D<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.expect
index c6802a78d3f..b25e9140fab 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.expect
@@ -2,13 +2,13 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::num* = core::num*> extends core::Object {
+class C<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* x;
   const constructor •(self::C::T* x) → self::C<self::C::T*>*
     : self::C::x = x, super core::Object::•()
     ;
 }
-class D<T extends core::num* = core::num*> extends core::Object {
+class D<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.transformed.expect
index c6802a78d3f..b25e9140fab 100644
--- a/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/constructors_infer_from_arguments_const_with_upper_bound.dart.strong.transformed.expect
@@ -2,13 +2,13 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::num* = core::num*> extends core::Object {
+class C<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   final field self::C::T* x;
   const constructor •(self::C::T* x) → self::C<self::C::T*>*
     : self::C::x = x, super core::Object::•()
     ;
 }
-class D<T extends core::num* = core::num*> extends core::Object {
+class D<T extends core::num* = core::num*> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.outline.expect
index 2aa6d597e76..7a7aebc2afa 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.expect
index 0fda0a1b732..9abd5f3844c 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.transformed.expect
index 0fda0a1b732..9abd5f3844c 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.outline.expect
index 5b2f6049d62..88aeaca224c 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.expect
index 8a2ff241bcd..b83b8fe101b 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.transformed.expect
index 8a2ff241bcd..b83b8fe101b 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_class_members.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.outline.expect
index e9ee04c9353..dcbe03a2cb8 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.expect
index 2a1ae246f1d..b9774d60a82 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.transformed.expect
index 7d1a7f36bf0..41a115ed291 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_for_loop_variable.dart.strong.transformed.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.outline.expect
index e9ee04c9353..dcbe03a2cb8 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.expect
index b93b09cd03c..bb1c4d6da00 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.transformed.expect
index b93b09cd03c..bb1c4d6da00 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.outline.expect
index 401d558b88c..6bf82757024 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(dynamic l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.expect
index cbdc206dd1a..ae2a9b67181 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(dynamic l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.transformed.expect
index cbdc206dd1a..ae2a9b67181 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_locals_referring_to_locals.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(dynamic l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.outline.expect
index 4c70c660a73..0a774f488d6 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.expect
index 2b285f43424..ecbef4260eb 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.transformed.expect
index 2b285f43424..ecbef4260eb 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.outline.expect
index e9ee04c9353..dcbe03a2cb8 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.expect
index 402205d6b02..f2402c002c4 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.transformed.expect
index 402205d6b02..f2402c002c4 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_parameter_local.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable.dart.outline.expect
index 74ed4894a26..ba150781368 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef F<unrelated T extends core::Object* = dynamic> = () →* void;
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.outline.expect
index e9ee04c9353..dcbe03a2cb8 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.expect
index c30db0b3a4a..b6183511f1a 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.transformed.expect
index c30db0b3a4a..b6183511f1a 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_type_variable_local.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.outline.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.outline.expect
index 1f341e92849..50ccca4df00 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.outline.expect
@@ -3,7 +3,7 @@ import self as self;
 import "dart:core" as core;
 
 typedef F = () →* void;
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.expect
index 8e70fef8dda..c31b27b4dcf 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.expect
@@ -4,7 +4,7 @@ import "dart:core" as core;
 
 @#C1
 typedef F = () →* void;
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.transformed.expect
index 8e70fef8dda..c31b27b4dcf 100644
--- a/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/downwards_inference_annotations_typedef.dart.strong.transformed.expect
@@ -4,7 +4,7 @@ import "dart:core" as core;
 
 @#C1
 typedef F = () →* void;
-class Foo extends core::Object {
+class Foo extends core::Object /*hasConstConstructor*/  {
   const constructor •(core::List<core::String*>* l) → self::Foo*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.outline.expect b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.outline.expect
index 33d450e2528..75fcb77da0e 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.outline.expect
@@ -33,7 +33,7 @@ class F extends core::Object implements self::B {
   synthetic constructor •() → self::F*
     ;
 }
-abstract class _G&Object&B = core::Object with self::B {
+abstract class _G&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.expect b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.expect
index a6eac70b022..37866ab510b 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.expect
@@ -39,7 +39,7 @@ class F extends core::Object implements self::B {
     : super core::Object::•()
     ;
 }
-abstract class _G&Object&B = core::Object with self::B {
+abstract class _G&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.transformed.expect
index f2ba8daab0a..ae76c807861 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_getter.dart.strong.transformed.expect
@@ -39,7 +39,7 @@ class F extends core::Object implements self::B {
     : super core::Object::•()
     ;
 }
-abstract class _G&Object&B extends core::Object implements self::B {
+abstract class _G&Object&B extends core::Object implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.outline.expect b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.outline.expect
index f3a0cea5d9a..496e5d96fc1 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.outline.expect
@@ -33,7 +33,7 @@ class F extends core::Object implements self::B {
   synthetic constructor •() → self::F*
     ;
 }
-abstract class _G&Object&B = core::Object with self::B {
+abstract class _G&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.expect b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.expect
index 15bcc2ce6cc..f22d6793466 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.expect
@@ -38,7 +38,7 @@ class F extends core::Object implements self::B {
     : super core::Object::•()
     ;
 }
-abstract class _G&Object&B = core::Object with self::B {
+abstract class _G&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.transformed.expect
index 485fda26e8b..92238fe9bc4 100644
--- a/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/infer_field_overrides_setter.dart.strong.transformed.expect
@@ -38,7 +38,7 @@ class F extends core::Object implements self::B {
     : super core::Object::•()
     ;
 }
-abstract class _G&Object&B extends core::Object implements self::B {
+abstract class _G&Object&B extends core::Object implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_G&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.outline.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.outline.expect
index f7f66a76018..e528298eca3 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.outline.expect
@@ -7,7 +7,7 @@ abstract class I<E extends core::Object* = dynamic> extends core::Object {
     ;
   abstract method m(dynamic a, (dynamic, self::I::E*) →* core::String* f) → core::String*;
 }
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> /*hasConstConstructor*/  {
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
     ;
@@ -18,7 +18,7 @@ abstract class M extends core::Object {
   synthetic constructor •() → self::M*
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.expect
index fcd1d67fb04..235db8a94ca 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.expect
@@ -15,7 +15,7 @@ abstract class I<E extends core::Object* = dynamic> extends core::Object {
     ;
   abstract method m(dynamic a, (dynamic, self::I::E*) →* core::String* f) → core::String*;
 }
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> /*hasConstConstructor*/  {
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
     ;
@@ -27,7 +27,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.transformed.expect
index fcd1d67fb04..235db8a94ca 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_5.dart.strong.transformed.expect
@@ -15,7 +15,7 @@ abstract class I<E extends core::Object* = dynamic> extends core::Object {
     ;
   abstract method m(dynamic a, (dynamic, self::I::E*) →* core::String* f) → core::String*;
 }
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<self::A::E*> /*hasConstConstructor*/  {
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
     ;
@@ -27,7 +27,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.outline.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.outline.expect
index d10152aeaef..ae2e3bdd109 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.outline.expect
@@ -5,7 +5,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as inf;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> /*hasConstConstructor*/  {
   final field self::A::E* value = null;
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
@@ -16,7 +16,7 @@ abstract class M extends core::Object {
   synthetic constructor •() → self::M*
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.expect
index 62bff19b740..c6c1c34ae2d 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.expect
@@ -12,7 +12,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as inf;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> /*hasConstConstructor*/  {
   final field self::A::E* value = null;
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
@@ -24,7 +24,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.transformed.expect
index 62bff19b740..c6c1c34ae2d 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle.dart.strong.transformed.expect
@@ -12,7 +12,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as inf;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements inf::I<self::A::E*> /*hasConstConstructor*/  {
   final field self::A::E* value = null;
   const constructor •() → self::A<self::A::E*>*
     : super core::Object::•()
@@ -24,7 +24,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M {
+class B<E extends core::Object* = dynamic> extends self::A<self::B::E*> implements self::M /*hasConstConstructor*/  {
   const constructor •() → self::B<self::B::E*>*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.outline.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.outline.expect
index 4b3a0522bf8..deae9bd165e 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.outline.expect
@@ -20,7 +20,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as self;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> /*hasConstConstructor*/  {
   final field test::A::E* value = null;
   const constructor •() → test::A<test::A::E*>*
     : super core::Object::•()
@@ -31,7 +31,7 @@ abstract class M extends core::Object {
   synthetic constructor •() → test::M*
     ;
 }
-class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M {
+class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M /*hasConstConstructor*/  {
   const constructor •() → test::B<test::B::E*>*
     : super test::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.expect
index fe2a499da73..94b0561f4f4 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.expect
@@ -27,7 +27,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as self;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> /*hasConstConstructor*/  {
   final field test::A::E* value = null;
   const constructor •() → test::A<test::A::E*>*
     : super core::Object::•()
@@ -39,7 +39,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M {
+class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M /*hasConstConstructor*/  {
   const constructor •() → test::B<test::B::E*>*
     : super test::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.transformed.expect
index fe2a499da73..94b0561f4f4 100644
--- a/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/infer_types_on_generic_instantiations_in_library_cycle_a.dart.strong.transformed.expect
@@ -27,7 +27,7 @@ import "infer_types_on_generic_instantiations_in_library_cycle_a.dart" as self;
 
 import "org-dartlang-testcase:///infer_types_on_generic_instantiations_in_library_cycle_a.dart";
 
-abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> {
+abstract class A<E extends core::Object* = dynamic> extends core::Object implements self::I<test::A::E*> /*hasConstConstructor*/  {
   final field test::A::E* value = null;
   const constructor •() → test::A<test::A::E*>*
     : super core::Object::•()
@@ -39,7 +39,7 @@ abstract class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M {
+class B<E extends core::Object* = dynamic> extends test::A<test::B::E*> implements test::M /*hasConstConstructor*/  {
   const constructor •() → test::B<test::B::E*>*
     : super test::A::•()
     ;
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.outline.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.outline.expect
index f34fca16206..b62af694ad6 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = const <self::E*>[self::E::v1];
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.expect
index 54268ceb82e..0ea8ae216c7 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C4;
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.transformed.expect
index 54268ceb82e..0ea8ae216c7 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C4;
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.outline.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.outline.expect
index c337f19d306..21b71462879 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = const <self::E*>[self::E::v1];
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.expect
index 8286aa9b13e..908dd56716d 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C4;
diff --git a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.transformed.expect
index 8286aa9b13e..908dd56716d 100644
--- a/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/inferred_type_is_enum_values.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class E extends core::Object {
+class E extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::E*>* values = #C4;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.outline.expect
index 07c3f610285..4c1c9339537 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.outline.expect
@@ -14,7 +14,7 @@ class M1 extends core::Object implements self::I<core::int*> {
   synthetic constructor •() → self::M1*
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::String*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::String*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.expect
index 826dbaa9f3e..40471812f81 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.expect
@@ -17,7 +17,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::String*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::String*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.transformed.expect
index ce826f6f457..93f81eda8b0 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_1.dart.strong.transformed.expect
@@ -17,7 +17,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::String*> {
+abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::String*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.outline.expect
index 6ad60a02c57..eea31bfb9ee 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.outline.expect
@@ -14,7 +14,7 @@ class M1 extends core::Object implements self::I<core::int*> {
   synthetic constructor •() → self::M1*
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::int*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.expect
index 15a2b6c07ee..80e9549e887 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.expect
@@ -17,7 +17,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::int*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.transformed.expect
index dd85f9ff59a..af9251c85fe 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_2.dart.strong.transformed.expect
@@ -17,7 +17,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::int*> {
+abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.outline.expect
index e769695eff2..66697a5a25a 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.outline.expect
@@ -26,7 +26,7 @@ class M1 extends core::Object implements self::I<core::int*> {
   synthetic constructor •() → self::M1*
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::Comparable<dynamic>*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::Comparable<dynamic>*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.expect
index e44fcb9846e..7206b5a395f 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.expect
@@ -29,7 +29,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::Comparable<dynamic>*> {
+abstract class _A&M1&M0 = self::M1 with self::M0<core::int*, core::Comparable<dynamic>*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.transformed.expect
index d17f94c12db..b4286e89578 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_instantiate_to_bounds_3.dart.strong.transformed.expect
@@ -29,7 +29,7 @@ class M1 extends core::Object implements self::I<core::int*> {
     : super core::Object::•()
     ;
 }
-abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::Comparable<dynamic>*> {
+abstract class _A&M1&M0 extends self::M1 implements self::M0<core::int*, core::Comparable<dynamic>*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M1&M0*
     : super self::M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.outline.expect
index c0a8ae0728c..7bcc04edc49 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.outline.expect
@@ -10,7 +10,7 @@ class J<X extends core::Object* = dynamic> extends core::Object {
   synthetic constructor •() → self::J<self::J::X*>*
     ;
 }
-abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> = self::I<self::_M0&I&J::X*> with self::J<self::_M0&I&J::Y*> {
+abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> = self::I<self::_M0&I&J::X*> with self::J<self::_M0&I&J::Y*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_M0&I&J<self::_M0&I&J::X*, self::_M0&I&J::Y*>*
     : super self::I::•()
     ;
@@ -27,7 +27,7 @@ class M2 extends self::M1 implements self::J<core::double*> {
   synthetic constructor •() → self::M2*
     ;
 }
-abstract class _A&M2&M0 = self::M2 with self::M0<core::int*, core::double*> {
+abstract class _A&M2&M0 = self::M2 with self::M0<core::int*, core::double*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.expect
index a7ffa02bdf7..a7002907014 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.expect
@@ -12,7 +12,7 @@ class J<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> = self::I<self::_M0&I&J::X*> with self::J<self::_M0&I&J::Y*> {
+abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> = self::I<self::_M0&I&J::X*> with self::J<self::_M0&I&J::Y*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_M0&I&J<self::_M0&I&J::X*, self::_M0&I&J::Y*>*
     : super self::I::•()
     ;
@@ -32,7 +32,7 @@ class M2 extends self::M1 implements self::J<core::double*> {
     : super self::M1::•()
     ;
 }
-abstract class _A&M2&M0 = self::M2 with self::M0<core::int*, core::double*> {
+abstract class _A&M2&M0 = self::M2 with self::M0<core::int*, core::double*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.transformed.expect
index c25154e4db8..847459dcc14 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_multiple_constraints.dart.strong.transformed.expect
@@ -12,7 +12,7 @@ class J<X extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> extends self::I<self::_M0&I&J::X*> implements self::J<self::_M0&I&J::Y*> {
+abstract class _M0&I&J<X extends core::Object* = dynamic, Y extends core::Object* = dynamic> extends self::I<self::_M0&I&J::X*> implements self::J<self::_M0&I&J::Y*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_M0&I&J<self::_M0&I&J::X*, self::_M0&I&J::Y*>*
     : super self::I::•()
     ;
@@ -32,7 +32,7 @@ class M2 extends self::M1 implements self::J<core::double*> {
     : super self::M1::•()
     ;
 }
-abstract class _A&M2&M0 extends self::M2 implements self::M0<core::int*, core::double*> {
+abstract class _A&M2&M0 extends self::M2 implements self::M0<core::int*, core::double*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.outline.expect
index 6c5c37807b8..6cc10f5f631 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.outline.expect
@@ -18,7 +18,7 @@ class M2<T extends core::Object* = dynamic> extends self::M1<core::Map<self::M2:
   synthetic constructor •() → self::M2<self::M2::T*>*
     ;
 }
-abstract class _A&M2&M0 = self::M2<core::int*> with self::M0<core::Map<core::int*, core::int*>*> {
+abstract class _A&M2&M0 = self::M2<core::int*> with self::M0<core::Map<core::int*, core::int*>*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.expect
index 3512c8c9fc1..ced4a8dfdbf 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.expect
@@ -22,7 +22,7 @@ class M2<T extends core::Object* = dynamic> extends self::M1<core::Map<self::M2:
     : super self::M1::•()
     ;
 }
-abstract class _A&M2&M0 = self::M2<core::int*> with self::M0<core::Map<core::int*, core::int*>*> {
+abstract class _A&M2&M0 = self::M2<core::int*> with self::M0<core::Map<core::int*, core::int*>*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.transformed.expect
index 62478671840..2ddd62d23f2 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_non_trivial_constraints.dart.strong.transformed.expect
@@ -22,7 +22,7 @@ class M2<T extends core::Object* = dynamic> extends self::M1<core::Map<self::M2:
     : super self::M1::•()
     ;
 }
-abstract class _A&M2&M0 extends self::M2<core::int*> implements self::M0<core::Map<core::int*, core::int*>*> {
+abstract class _A&M2&M0 extends self::M2<core::int*> implements self::M0<core::Map<core::int*, core::int*>*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M2&M0*
     : super self::M2::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.outline.expect
index 5f56095cf85..c8dd799ae19 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.outline.expect
@@ -14,7 +14,7 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
   synthetic constructor •() → self::M1<self::M1::T*>*
     ;
 }
-abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> {
+abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.expect
index 62f31c18e3b..f773d9bad8d 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.expect
@@ -17,7 +17,7 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> {
+abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.transformed.expect
index 31c23b959b8..c4c5d7847ff 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_1.dart.strong.transformed.expect
@@ -17,7 +17,7 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&M0&M1 extends self::M0<core::int*> implements self::M1<core::int*> {
+abstract class _A&M0&M1 extends self::M0<core::int*> implements self::M1<core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.outline.expect
index 523042e0439..059aa18fa62 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.outline.expect
@@ -18,12 +18,12 @@ class M2<T extends core::Object* = dynamic> extends self::I<self::M2::T*> {
   synthetic constructor •() → self::M2<self::M2::T*>*
     ;
 }
-abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> {
+abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
 }
-abstract class _A&M0&M1&M2 = self::_A&M0&M1 with self::M2<core::int*> {
+abstract class _A&M0&M1&M2 = self::_A&M0&M1 with self::M2<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1&M2*
     : super self::_A&M0&M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.expect
index 2ed4120acf7..7fd2d2ec4e0 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.expect
@@ -22,12 +22,12 @@ class M2<T extends core::Object* = dynamic> extends self::I<self::M2::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> {
+abstract class _A&M0&M1 = self::M0<core::int*> with self::M1<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
 }
-abstract class _A&M0&M1&M2 = self::_A&M0&M1 with self::M2<core::int*> {
+abstract class _A&M0&M1&M2 = self::_A&M0&M1 with self::M2<core::int*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&M0&M1&M2*
     : super self::_A&M0&M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.transformed.expect
index d8f1efe5812..59d9df72e6e 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_2.dart.strong.transformed.expect
@@ -22,12 +22,12 @@ class M2<T extends core::Object* = dynamic> extends self::I<self::M2::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&M0&M1 extends self::M0<core::int*> implements self::M1<core::int*> {
+abstract class _A&M0&M1 extends self::M0<core::int*> implements self::M1<core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M0&M1*
     : super self::M0::•()
     ;
 }
-abstract class _A&M0&M1&M2 extends self::_A&M0&M1 implements self::M2<core::int*> {
+abstract class _A&M0&M1&M2 extends self::_A&M0&M1 implements self::M2<core::int*> /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_A&M0&M1&M2*
     : super self::_A&M0&M1::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.outline.expect
index d520fcdab82..4a322abe345 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.outline.expect
@@ -27,12 +27,12 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
   synthetic constructor •() → self::M1<self::M1::T*>*
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<core::int*> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<core::int*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.strong.expect
index 79557a6c7cc..439d8bfcabd 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_3.dart.strong.expect
@@ -30,12 +30,12 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<core::int*> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<core::int*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.outline.expect
index 1fed224a716..b4b8a61b02c 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.outline.expect
@@ -22,12 +22,12 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
   synthetic constructor •() → self::M1<self::M1::T*>*
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.strong.expect
index 26a475182f6..d0df383acfd 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_outwards_4.dart.strong.expect
@@ -25,12 +25,12 @@ class M1<T extends core::Object* = dynamic> extends self::I<self::M1::T*> {
     : super self::I::•()
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.outline.expect
index 99909647af2..d440c3a99b5 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.outline.expect
@@ -27,12 +27,12 @@ class M1<T extends core::Object* = dynamic> extends core::Object implements self
   synthetic constructor •() → self::M1<self::M1::T*>*
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.strong.expect
index 468cb8ced10..2643b49fb09 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_unification_1.dart.strong.expect
@@ -30,12 +30,12 @@ class M1<T extends core::Object* = dynamic> extends core::Object implements self
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.outline.expect b/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.outline.expect
index acf7065b6de..946f92c07cd 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.outline.expect
@@ -29,12 +29,12 @@ class M1<T extends core::Object* = dynamic> extends core::Object implements self
   synthetic constructor •() → self::M1<self::M1::T*>*
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.strong.expect b/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.strong.expect
index 47897de6ac7..9389ac6bd86 100644
--- a/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/mixin_inference_unification_2.dart.strong.expect
@@ -32,12 +32,12 @@ class M1<T extends core::Object* = dynamic> extends core::Object implements self
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0 = core::Object with self::M0<dynamic> {
+abstract class _A&Object&M0 = core::Object with self::M0<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> {
+abstract class _A&Object&M0&M1 = self::_A&Object&M0 with self::M1<dynamic> /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M0&M1*
     : super self::_A&Object&M0::•()
     ;
diff --git a/pkg/front_end/testcases/inference/non_const_invocation.dart.outline.expect b/pkg/front_end/testcases/inference/non_const_invocation.dart.outline.expect
index 1ce9cd4a669..0209712afed 100644
--- a/pkg/front_end/testcases/inference/non_const_invocation.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/non_const_invocation.dart.outline.expect
@@ -25,7 +25,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     ;
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.expect b/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.expect
index 310bddfdac6..d38852e8458 100644
--- a/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.expect
+++ b/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.expect
@@ -26,7 +26,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     return <self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>{};
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.transformed.expect b/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.transformed.expect
index 310bddfdac6..d38852e8458 100644
--- a/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference/non_const_invocation.dart.strong.transformed.expect
@@ -26,7 +26,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     return <self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>{};
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/const_invocation.dart.outline.expect b/pkg/front_end/testcases/inference_new/const_invocation.dart.outline.expect
index 1ce9cd4a669..0209712afed 100644
--- a/pkg/front_end/testcases/inference_new/const_invocation.dart.outline.expect
+++ b/pkg/front_end/testcases/inference_new/const_invocation.dart.outline.expect
@@ -25,7 +25,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     ;
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.expect b/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.expect
index 68950968d07..f5712f51461 100644
--- a/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.expect
+++ b/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.expect
@@ -26,7 +26,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     return #C10;
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.transformed.expect b/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.transformed.expect
index 68950968d07..f5712f51461 100644
--- a/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference_new/const_invocation.dart.strong.transformed.expect
@@ -26,7 +26,7 @@ class Foo<T extends core::Object* = dynamic> extends core::Object {
   get v9() → core::Map<self::Foo::T*, (self::Foo::T*) →* self::Foo::T*>*
     return #C10;
 }
-class Bar<T extends core::Object* = dynamic> extends core::Object {
+class Bar<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::Bar<self::Bar::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/switch.dart.outline.expect b/pkg/front_end/testcases/inference_new/switch.dart.outline.expect
index 24795714745..ccbc21c8170 100644
--- a/pkg/front_end/testcases/inference_new/switch.dart.outline.expect
+++ b/pkg/front_end/testcases/inference_new/switch.dart.outline.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/switch.dart.strong.expect b/pkg/front_end/testcases/inference_new/switch.dart.strong.expect
index f3d6d7797eb..8d636a22b1c 100644
--- a/pkg/front_end/testcases/inference_new/switch.dart.strong.expect
+++ b/pkg/front_end/testcases/inference_new/switch.dart.strong.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/inference_new/switch.dart.strong.transformed.expect b/pkg/front_end/testcases/inference_new/switch.dart.strong.transformed.expect
index f3d6d7797eb..8d636a22b1c 100644
--- a/pkg/front_end/testcases/inference_new/switch.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference_new/switch.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library test;
 import self as self;
 import "dart:core" as core;
 
-class C<T extends core::Object* = dynamic> extends core::Object {
+class C<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C<self::C::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.outline.expect b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.outline.expect
index baafca822dc..aa555ba7543 100644
--- a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.expect b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.expect
index 461a137f4f9..3259378bdf9 100644
--- a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.transformed.expect
index 461a137f4f9..3259378bdf9 100644
--- a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.expect b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.expect
index 461a137f4f9..3259378bdf9 100644
--- a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.transformed.expect
index 461a137f4f9..3259378bdf9 100644
--- a/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/initializer_rewrite.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.outline.expect
index 52421816357..bd10355e5c3 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.expect
index c5a0a64923b..0cfc5740c9b 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.transformed.expect
index c5a0a64923b..0cfc5740c9b 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.expect
index c5a0a64923b..0cfc5740c9b 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.transformed.expect
index c5a0a64923b..0cfc5740c9b 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.outline.expect
index 9e91c1bbe61..e7882abdc3c 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.expect
index 51292183fb3..2a325537ccc 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.transformed.expect
index 51292183fb3..2a325537ccc 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.expect
index 51292183fb3..2a325537ccc 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.transformed.expect
index 51292183fb3..2a325537ccc 100644
--- a/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.outline.expect
index 9e91c1bbe61..e7882abdc3c 100644
--- a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.expect
index 2153b49ba98..cdd56ea6a30 100644
--- a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.transformed.expect
index 2153b49ba98..cdd56ea6a30 100644
--- a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.expect
index 2153b49ba98..cdd56ea6a30 100644
--- a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.transformed.expect
index 2153b49ba98..cdd56ea6a30 100644
--- a/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_final_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.outline.expect
index 54f0057388d..511d1012db1 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.expect
index 0c3e5d761da..a133a768412 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.transformed.expect
index 0c3e5d761da..a133a768412 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.expect
index 0c3e5d761da..a133a768412 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.transformed.expect
index 0c3e5d761da..a133a768412 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.outline.expect
index 8fb7e648a0f..2ed3a819bda 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.expect
index af2b2c370a8..3bea7e07532 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.transformed.expect
index af2b2c370a8..3bea7e07532 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.expect
index af2b2c370a8..3bea7e07532 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.transformed.expect
index af2b2c370a8..3bea7e07532 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.outline.expect
index 8fb7e648a0f..2ed3a819bda 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.expect
index a0dbc156c6b..26f06e04196 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.transformed.expect
index a0dbc156c6b..26f06e04196 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.expect
index a0dbc156c6b..26f06e04196 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.transformed.expect
index a0dbc156c6b..26f06e04196 100644
--- a/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/instance_nullable_final_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/issue40093.dart.outline.expect b/pkg/front_end/testcases/late_lowering/issue40093.dart.outline.expect
index 755fbeeca90..0606425ea42 100644
--- a/pkg/front_end/testcases/late_lowering/issue40093.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/issue40093.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method error() → dynamic
diff --git a/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.expect b/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.expect
index 27df1f833ee..551b8f09ea7 100644
--- a/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.transformed.expect
index 41e15036281..1f469d78abb 100644
--- a/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/issue40093.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.expect b/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.expect
index 27df1f833ee..551b8f09ea7 100644
--- a/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.transformed.expect
index 41e15036281..1f469d78abb 100644
--- a/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/issue40093.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.outline.expect
index 619e509e013..e0a070f45e2 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.expect
index 9b14dc5daa0..9e5e4e1f905 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.transformed.expect
index 9b14dc5daa0..9e5e4e1f905 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.expect
index 9b14dc5daa0..9e5e4e1f905 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.transformed.expect
index 9b14dc5daa0..9e5e4e1f905 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.outline.expect
index 6fd79a1d83f..10a2e030ab7 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.expect
index 126b0d7e12f..4d78e462e1e 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.transformed.expect
index 126b0d7e12f..4d78e462e1e 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.expect
index 126b0d7e12f..4d78e462e1e 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.transformed.expect
index 126b0d7e12f..4d78e462e1e 100644
--- a/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.outline.expect
index 274c943e3fc..1bf3e6767e9 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.expect
index 9c3f03740c8..ea54cfd4239 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.transformed.expect
index 9c3f03740c8..ea54cfd4239 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.expect
index 9c3f03740c8..ea54cfd4239 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.transformed.expect
index 9c3f03740c8..ea54cfd4239 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.outline.expect
index 35db6920fd8..dd0572a4a9e 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.expect
index 4499a18af5b..6c0bb202683 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.transformed.expect
index 4499a18af5b..6c0bb202683 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.expect
index 4499a18af5b..6c0bb202683 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.transformed.expect
index 4499a18af5b..6c0bb202683 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.outline.expect
index 81d34cffab1..681b16d20f6 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method main() → dynamic
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.expect
index 3ccf8920435..883b25a3e9f 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.transformed.expect
index 3ccf8920435..883b25a3e9f 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.expect
index 3ccf8920435..883b25a3e9f 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.transformed.expect
index 3ccf8920435..883b25a3e9f 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.outline.expect
index 9cba406e20b..02046fba52a 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.expect
index f4f95e3dd18..bb8676df9e7 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.transformed.expect
index f4f95e3dd18..bb8676df9e7 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.expect
index f4f95e3dd18..bb8676df9e7 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.transformed.expect
index f4f95e3dd18..bb8676df9e7 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_local_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.outline.expect
index e0b1ab58b4c..159d80f335c 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.expect
index 49d7ba3748f..aa8b4d17889 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.transformed.expect
index 49d7ba3748f..aa8b4d17889 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.expect
index 49d7ba3748f..aa8b4d17889 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.transformed.expect
index 49d7ba3748f..aa8b4d17889 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.outline.expect
index d67a9a2fde5..802698c20bf 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.expect
index db2ed0b4f1d..59a762a1e76 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.transformed.expect
index db2ed0b4f1d..59a762a1e76 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.expect
index db2ed0b4f1d..59a762a1e76 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.transformed.expect
index db2ed0b4f1d..59a762a1e76 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.outline.expect
index 81d34cffab1..681b16d20f6 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method main() → dynamic
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.expect
index c925621561c..dc6b6adaa5b 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.transformed.expect
index c925621561c..dc6b6adaa5b 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.expect
index c925621561c..dc6b6adaa5b 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.transformed.expect
index c925621561c..dc6b6adaa5b 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.outline.expect
index 9cba406e20b..02046fba52a 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.expect
index d1984d9b544..3d8ddf1760e 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.transformed.expect
index d1984d9b544..3d8ddf1760e 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.expect
index d1984d9b544..3d8ddf1760e 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.transformed.expect
index d1984d9b544..3d8ddf1760e 100644
--- a/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_final_nullable_local_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.outline.expect
index 81d34cffab1..681b16d20f6 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method main() → dynamic
diff --git a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.expect
index 363c9226181..25a50976982 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.transformed.expect
index 363c9226181..25a50976982 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.expect
index 363c9226181..25a50976982 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.transformed.expect
index 363c9226181..25a50976982 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.outline.expect
index 9cba406e20b..02046fba52a 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.expect
index 7f4cd1bbdf6..eaf2671f0c6 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.transformed.expect
index 7f4cd1bbdf6..eaf2671f0c6 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.expect
index 7f4cd1bbdf6..eaf2671f0c6 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.transformed.expect
index 7f4cd1bbdf6..eaf2671f0c6 100644
--- a/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_local_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.outline.expect
index 517b399ac1a..f377c7e29df 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.expect
index dbfe4779dcd..6a2319dda4a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.transformed.expect
index dbfe4779dcd..6a2319dda4a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.expect
index dbfe4779dcd..6a2319dda4a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.transformed.expect
index dbfe4779dcd..6a2319dda4a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.outline.expect
index d5e4386286c..b5c1e15b51d 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.expect
index e9709068f81..f0bc8b77a7c 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.transformed.expect
index e9709068f81..f0bc8b77a7c 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.expect
index e9709068f81..f0bc8b77a7c 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.transformed.expect
index e9709068f81..f0bc8b77a7c 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_field_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.outline.expect
index bccbe283389..cfc71b3254a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.expect
index 9363ab8c62a..25dee5aa8f9 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.transformed.expect
index 9363ab8c62a..25dee5aa8f9 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.expect
index 9363ab8c62a..25dee5aa8f9 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.transformed.expect
index 9363ab8c62a..25dee5aa8f9 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_with_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.outline.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.outline.expect
index 9cba406e20b..02046fba52a 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.expect
index 5b37f46d695..b31397132ee 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.transformed.expect
index 5b37f46d695..b31397132ee 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.expect
index 5b37f46d695..b31397132ee 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.transformed.expect
index 5b37f46d695..b31397132ee 100644
--- a/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/late_nullable_local_without_initializer.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/later.dart.outline.expect b/pkg/front_end/testcases/late_lowering/later.dart.outline.expect
index 25da1db50e5..7c07f789d6c 100644
--- a/pkg/front_end/testcases/late_lowering/later.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/later.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -26,7 +26,7 @@ class A extends core::Object {
   method foo(core::int x) → dynamic
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   field core::int? _#B#x = null;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/late_lowering/later.dart.strong.expect b/pkg/front_end/testcases/late_lowering/later.dart.strong.expect
index 1b470d9ce24..4646abeb0e6 100644
--- a/pkg/front_end/testcases/late_lowering/later.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/later.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -79,7 +79,7 @@ class A extends core::Object {
     this.{self::A::_#A#b} = #t2;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   field core::int? _#B#x = null;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/late_lowering/later.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/later.dart.strong.transformed.expect
index d54ab7be641..a0a15231a03 100644
--- a/pkg/front_end/testcases/late_lowering/later.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/later.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -79,7 +79,7 @@ class A extends core::Object {
     this.{self::A::_#A#b} = #t2;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   field core::int? _#B#x = null;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/late_lowering/later.dart.weak.expect b/pkg/front_end/testcases/late_lowering/later.dart.weak.expect
index f7e7212b75d..c886bcfeb06 100644
--- a/pkg/front_end/testcases/late_lowering/later.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/later.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -79,7 +79,7 @@ class A extends core::Object {
     this.{self::A::_#A#b} = #t2;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   field core::int? _#B#x = null;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/late_lowering/later.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/later.dart.weak.transformed.expect
index 3ae52e717ea..a7094a71bd7 100644
--- a/pkg/front_end/testcases/late_lowering/later.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/later.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -79,7 +79,7 @@ class A extends core::Object {
     this.{self::A::_#A#b} = #t2;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   field core::int? _#B#x = null;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/late_lowering/override.dart.outline.expect b/pkg/front_end/testcases/late_lowering/override.dart.outline.expect
index 35697bcd278..93117d170c0 100644
--- a/pkg/front_end/testcases/late_lowering/override.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/override.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/override.dart.strong.expect b/pkg/front_end/testcases/late_lowering/override.dart.strong.expect
index 2fb9901888f..8e2fcee5774 100644
--- a/pkg/front_end/testcases/late_lowering/override.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/override.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/override.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/override.dart.strong.transformed.expect
index 2fb9901888f..8e2fcee5774 100644
--- a/pkg/front_end/testcases/late_lowering/override.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/override.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/override.dart.weak.expect b/pkg/front_end/testcases/late_lowering/override.dart.weak.expect
index 2fb9901888f..8e2fcee5774 100644
--- a/pkg/front_end/testcases/late_lowering/override.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/override.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/override.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/override.dart.weak.transformed.expect
index 2fb9901888f..8e2fcee5774 100644
--- a/pkg/front_end/testcases/late_lowering/override.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/override.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "dart:_internal" as _in;
diff --git a/pkg/front_end/testcases/late_lowering/return_late.dart.outline.expect b/pkg/front_end/testcases/late_lowering/return_late.dart.outline.expect
index b09c8c1c786..00f47083ef3 100644
--- a/pkg/front_end/testcases/late_lowering/return_late.dart.outline.expect
+++ b/pkg/front_end/testcases/late_lowering/return_late.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/return_late.dart.strong.expect b/pkg/front_end/testcases/late_lowering/return_late.dart.strong.expect
index 2a0856488e5..7b6d3801f61 100644
--- a/pkg/front_end/testcases/late_lowering/return_late.dart.strong.expect
+++ b/pkg/front_end/testcases/late_lowering/return_late.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/return_late.dart.strong.transformed.expect b/pkg/front_end/testcases/late_lowering/return_late.dart.strong.transformed.expect
index 2a0856488e5..7b6d3801f61 100644
--- a/pkg/front_end/testcases/late_lowering/return_late.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/return_late.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/return_late.dart.weak.expect b/pkg/front_end/testcases/late_lowering/return_late.dart.weak.expect
index 2a0856488e5..7b6d3801f61 100644
--- a/pkg/front_end/testcases/late_lowering/return_late.dart.weak.expect
+++ b/pkg/front_end/testcases/late_lowering/return_late.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/late_lowering/return_late.dart.weak.transformed.expect b/pkg/front_end/testcases/late_lowering/return_late.dart.weak.transformed.expect
index 2a0856488e5..7b6d3801f61 100644
--- a/pkg/front_end/testcases/late_lowering/return_late.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/late_lowering/return_late.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/new_const_insertion/simple.dart.outline.expect b/pkg/front_end/testcases/new_const_insertion/simple.dart.outline.expect
index 5092f400b33..97237ce9ecb 100644
--- a/pkg/front_end/testcases/new_const_insertion/simple.dart.outline.expect
+++ b/pkg/front_end/testcases/new_const_insertion/simple.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* x;
   const constructor •(core::int* x) → self::A*
     : self::A::x = x, super core::Object::•()
diff --git a/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.expect b/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.expect
index 60b3c971f0d..4b21762e2bb 100644
--- a/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.expect
+++ b/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* x;
   const constructor •(core::int* x) → self::A*
     : self::A::x = x, super core::Object::•()
diff --git a/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.transformed.expect b/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.transformed.expect
index 60b3c971f0d..4b21762e2bb 100644
--- a/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/new_const_insertion/simple.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   final field core::int* x;
   const constructor •(core::int* x) → self::A*
     : self::A::x = x, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.outline.expect b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.outline.expect
index 0d1231813df..2602561e812 100644
--- a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.expect b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.expect
index ee9e3f66c24..88ac3aecd6f 100644
--- a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.transformed.expect
index ee9e3f66c24..88ac3aecd6f 100644
--- a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.expect b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.expect
index ee9e3f66c24..88ac3aecd6f 100644
--- a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.transformed.expect
index ee9e3f66c24..88ac3aecd6f 100644
--- a/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/assign_type_variable.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assignability.dart.outline.expect b/pkg/front_end/testcases/nnbd/assignability.dart.outline.expect
index 14b99fd0054..5697d0bc5cb 100644
--- a/pkg/front_end/testcases/nnbd/assignability.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/assignability.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/assignability.dart.strong.expect b/pkg/front_end/testcases/nnbd/assignability.dart.strong.expect
index 803bc0abbb3..9c3d4533a71 100644
--- a/pkg/front_end/testcases/nnbd/assignability.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/assignability.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/assignability.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/assignability.dart.strong.transformed.expect
index 803bc0abbb3..9c3d4533a71 100644
--- a/pkg/front_end/testcases/nnbd/assignability.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/assignability.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/assignability.dart.weak.expect b/pkg/front_end/testcases/nnbd/assignability.dart.weak.expect
index 55036c659ff..ddfc6a42f13 100644
--- a/pkg/front_end/testcases/nnbd/assignability.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/assignability.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/assignability.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/assignability.dart.weak.transformed.expect
index 55036c659ff..ddfc6a42f13 100644
--- a/pkg/front_end/testcases/nnbd/assignability.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/assignability.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/call.dart.outline.expect b/pkg/front_end/testcases/nnbd/call.dart.outline.expect
index 4b7665cf539..49f525c4d27 100644
--- a/pkg/front_end/testcases/nnbd/call.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/call.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/call.dart.strong.expect b/pkg/front_end/testcases/nnbd/call.dart.strong.expect
index 93617a26bc0..886ef644b25 100644
--- a/pkg/front_end/testcases/nnbd/call.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/call.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/call.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/call.dart.strong.transformed.expect
index 93617a26bc0..886ef644b25 100644
--- a/pkg/front_end/testcases/nnbd/call.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/call.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/call.dart.weak.expect b/pkg/front_end/testcases/nnbd/call.dart.weak.expect
index 88fb216a2a7..855a8911ccb 100644
--- a/pkg/front_end/testcases/nnbd/call.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/call.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/call.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/call.dart.weak.transformed.expect
index 88fb216a2a7..855a8911ccb 100644
--- a/pkg/front_end/testcases/nnbd/call.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/call.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/constants.dart.outline.expect b/pkg/front_end/testcases/nnbd/constants.dart.outline.expect
index ff2d8651094..d046e9f962d 100644
--- a/pkg/front_end/testcases/nnbd/constants.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/constants.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "constants_lib.dart" as con;
@@ -43,7 +43,7 @@ import "dart:core" as core;
 
 typedef F1<invariant T extends core::Object* = dynamic> = (T*) →* T*;
 typedef F2 = <T extends core::Object* = dynamic>(T*) →* T*;
-class Class<T extends core::Object* = dynamic> extends core::Object {
+class Class<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field con::Class::T* field;
   const constructor •(con::Class::T* field) → con::Class<con::Class::T*>*
     : con::Class::field = field, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/constants.dart.strong.expect b/pkg/front_end/testcases/nnbd/constants.dart.strong.expect
index c787b65e085..12632c38e21 100644
--- a/pkg/front_end/testcases/nnbd/constants.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/constants.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -99,7 +99,7 @@ import "dart:core" as core;
 
 typedef F1<invariant T extends core::Object* = dynamic> = (T*) →* T*;
 typedef F2 = <T extends core::Object* = dynamic>(T*) →* T*;
-class Class<T extends core::Object* = dynamic> extends core::Object {
+class Class<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field con::Class::T* field;
   const constructor •(con::Class::T* field) → con::Class<con::Class::T*>*
     : con::Class::field = field, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/constants.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/constants.dart.strong.transformed.expect
index c787b65e085..12632c38e21 100644
--- a/pkg/front_end/testcases/nnbd/constants.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/constants.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -99,7 +99,7 @@ import "dart:core" as core;
 
 typedef F1<invariant T extends core::Object* = dynamic> = (T*) →* T*;
 typedef F2 = <T extends core::Object* = dynamic>(T*) →* T*;
-class Class<T extends core::Object* = dynamic> extends core::Object {
+class Class<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field con::Class::T* field;
   const constructor •(con::Class::T* field) → con::Class<con::Class::T*>*
     : con::Class::field = field, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/constants.dart.weak.expect b/pkg/front_end/testcases/nnbd/constants.dart.weak.expect
index fdb1f8ebed4..794e075d9da 100644
--- a/pkg/front_end/testcases/nnbd/constants.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/constants.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -96,7 +96,7 @@ import "dart:core" as core;
 
 typedef F1<invariant T extends core::Object* = dynamic> = (T*) →* T*;
 typedef F2 = <T extends core::Object* = dynamic>(T*) →* T*;
-class Class<T extends core::Object* = dynamic> extends core::Object {
+class Class<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field con::Class::T* field;
   const constructor •(con::Class::T* field) → con::Class<con::Class::T*>*
     : con::Class::field = field, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/constants.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/constants.dart.weak.transformed.expect
index fdb1f8ebed4..794e075d9da 100644
--- a/pkg/front_end/testcases/nnbd/constants.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/constants.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -96,7 +96,7 @@ import "dart:core" as core;
 
 typedef F1<invariant T extends core::Object* = dynamic> = (T*) →* T*;
 typedef F2 = <T extends core::Object* = dynamic>(T*) →* T*;
-class Class<T extends core::Object* = dynamic> extends core::Object {
+class Class<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field con::Class::T* field;
   const constructor •(con::Class::T* field) → con::Class<con::Class::T*>*
     : con::Class::field = field, super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.outline.expect b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.outline.expect
index 7dc40d129fd..3c5a7aedcd3 100644
--- a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.expect b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.expect
index c56d12d8c17..53eae94bedd 100644
--- a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.transformed.expect
index c56d12d8c17..53eae94bedd 100644
--- a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.expect b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.expect
index c56d12d8c17..53eae94bedd 100644
--- a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.transformed.expect
index c56d12d8c17..53eae94bedd 100644
--- a/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/definite_assignment_and_completion.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.outline.expect b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.outline.expect
index c33f97f59b1..bffcb5fe9a4 100644
--- a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.expect b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.expect
index 3dac54e1e2d..fe5b9b3c3ae 100644
--- a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.transformed.expect
index 3dac54e1e2d..fe5b9b3c3ae 100644
--- a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.expect b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.expect
index 3dac54e1e2d..fe5b9b3c3ae 100644
--- a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.transformed.expect
index 3dac54e1e2d..fe5b9b3c3ae 100644
--- a/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/demote_closure_types.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.outline.expect b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.outline.expect
index 6f8ee3224cb..3847c08b79e 100644
--- a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -162,7 +162,7 @@ class Boo extends core::Object {
   synthetic constructor •() → self::Boo
     ;
 }
-abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Coo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -179,7 +179,7 @@ class Eoo extends core::Object implements self::Boo {
   synthetic constructor •() → self::Eoo
     ;
 }
-abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -193,7 +193,7 @@ class Goo = self::Boo with self::Aoo {
     : super self::Boo::•()
     ;
 }
-abstract class _Hoo&Object&Aoo = core::Object with self::Aoo {
+abstract class _Hoo&Object&Aoo = core::Object with self::Aoo /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hoo&Object&Aoo
     : super core::Object::•()
     ;
@@ -207,7 +207,7 @@ class Ioo = core::Object with self::Aoo implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Joo&Boo&Never extends self::Boo {
+abstract class _Joo&Boo&Never extends self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Joo&Boo&Never
     : super self::Boo::•()
     ;
@@ -224,29 +224,29 @@ class Loo extends core::Object {
   synthetic constructor •() → self::Loo
     ;
 }
-abstract class Moo1 extends self::Aoo implements self::Boo {
+abstract class Moo1 extends self::Aoo implements self::Boo /*isMixinDeclaration*/  {
 }
-abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo {
+abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo2&Aoo&Boo
     ;
 }
-abstract class Moo2 extends self::_Moo2&Aoo&Boo {
+abstract class Moo2 extends self::_Moo2&Aoo&Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo3 extends core::Object implements self::Aoo, self::Boo {
+abstract class Moo3 extends core::Object implements self::Aoo, self::Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo4 extends self::Aoo {
+abstract class Moo4 extends self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo {
+abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo5&Aoo&Never
     ;
 }
-abstract class Moo5 extends self::_Moo5&Aoo&Never {
+abstract class Moo5 extends self::_Moo5&Aoo&Never /*isMixinDeclaration*/  {
 }
-abstract class Moo6 extends core::Object {
+abstract class Moo6 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class Moo7 extends core::Object implements self::Aoo {
+abstract class Moo7 extends core::Object implements self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class Moo8 extends core::Object {
+abstract class Moo8 extends core::Object /*isMixinDeclaration*/  {
 }
 class Noo = core::Object with self::Aoo {
   synthetic constructor •() → self::Noo
diff --git a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.expect b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.expect
index a48c33f90db..443c33ee16a 100644
--- a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -164,7 +164,7 @@ class Boo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Coo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -184,7 +184,7 @@ class Eoo extends core::Object implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -199,7 +199,7 @@ class Goo = self::Boo with self::Aoo {
     : super self::Boo::•()
     ;
 }
-abstract class _Hoo&Object&Aoo = core::Object with self::Aoo {
+abstract class _Hoo&Object&Aoo = core::Object with self::Aoo /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hoo&Object&Aoo
     : super core::Object::•()
     ;
@@ -214,7 +214,7 @@ class Ioo = core::Object with self::Aoo implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Joo&Boo&Never extends self::Boo {
+abstract class _Joo&Boo&Never extends self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Joo&Boo&Never
     : super self::Boo::•()
     ;
@@ -234,31 +234,31 @@ class Loo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Moo1 extends self::Aoo implements self::Boo {
+abstract class Moo1 extends self::Aoo implements self::Boo /*isMixinDeclaration*/  {
 }
-abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo {
+abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo2&Aoo&Boo
     : super core::Object::•()
     ;
 }
-abstract class Moo2 extends self::_Moo2&Aoo&Boo {
+abstract class Moo2 extends self::_Moo2&Aoo&Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo3 extends core::Object implements self::Aoo, self::Boo {
+abstract class Moo3 extends core::Object implements self::Aoo, self::Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo4 extends self::Aoo {
+abstract class Moo4 extends self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo {
+abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo5&Aoo&Never
     : super core::Object::•()
     ;
 }
-abstract class Moo5 extends self::_Moo5&Aoo&Never {
+abstract class Moo5 extends self::_Moo5&Aoo&Never /*isMixinDeclaration*/  {
 }
-abstract class Moo6 extends core::Object {
+abstract class Moo6 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class Moo7 extends core::Object implements self::Aoo {
+abstract class Moo7 extends core::Object implements self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class Moo8 extends core::Object {
+abstract class Moo8 extends core::Object /*isMixinDeclaration*/  {
 }
 class Noo = core::Object with self::Aoo {
   synthetic constructor •() → self::Noo
diff --git a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.transformed.expect
index e46d7ae6356..d14af9b3518 100644
--- a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -164,7 +164,7 @@ class Boo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Coo&Boo&Aoo extends self::Boo implements self::Aoo {
+abstract class _Coo&Boo&Aoo extends self::Boo implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Coo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -184,7 +184,7 @@ class Eoo extends core::Object implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&Boo&Aoo extends self::Boo implements self::Aoo {
+abstract class _Foo&Boo&Aoo extends self::Boo implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Foo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -194,12 +194,12 @@ class Foo extends self::_Foo&Boo&Aoo {
     : super self::_Foo&Boo&Aoo::•()
     ;
 }
-class Goo extends self::Boo implements self::Aoo {
+class Goo extends self::Boo implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Goo
     : super self::Boo::•()
     ;
 }
-abstract class _Hoo&Object&Aoo extends core::Object implements self::Aoo {
+abstract class _Hoo&Object&Aoo extends core::Object implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hoo&Object&Aoo
     : super core::Object::•()
     ;
@@ -209,12 +209,12 @@ class Hoo extends self::_Hoo&Object&Aoo implements self::Boo {
     : super self::_Hoo&Object&Aoo::•()
     ;
 }
-class Ioo extends core::Object implements self::Boo, self::Aoo {
+class Ioo extends core::Object implements self::Boo, self::Aoo /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Ioo
     : super core::Object::•()
     ;
 }
-abstract class _Joo&Boo&Never extends self::Boo {
+abstract class _Joo&Boo&Never extends self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Joo&Boo&Never
     : super self::Boo::•()
     ;
@@ -234,43 +234,43 @@ class Loo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Moo1 extends self::Aoo implements self::Boo {
+abstract class Moo1 extends self::Aoo implements self::Boo /*isMixinDeclaration*/  {
 }
-abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo {
+abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo2&Aoo&Boo
     : super core::Object::•()
     ;
 }
-abstract class Moo2 extends self::_Moo2&Aoo&Boo {
+abstract class Moo2 extends self::_Moo2&Aoo&Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo3 extends core::Object implements self::Aoo, self::Boo {
+abstract class Moo3 extends core::Object implements self::Aoo, self::Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo4 extends self::Aoo {
+abstract class Moo4 extends self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo {
+abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo5&Aoo&Never
     : super core::Object::•()
     ;
 }
-abstract class Moo5 extends self::_Moo5&Aoo&Never {
+abstract class Moo5 extends self::_Moo5&Aoo&Never /*isMixinDeclaration*/  {
 }
-abstract class Moo6 extends core::Object {
+abstract class Moo6 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class Moo7 extends core::Object implements self::Aoo {
+abstract class Moo7 extends core::Object implements self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class Moo8 extends core::Object {
+abstract class Moo8 extends core::Object /*isMixinDeclaration*/  {
 }
-class Noo extends core::Object implements self::Aoo {
+class Noo extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Noo
     : super core::Object::•()
     ;
 }
-class NooDynamic extends core::Object implements self::Aoo {
+class NooDynamic extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::NooDynamic
     : super core::Object::•()
     ;
 }
-class NooVoid extends core::Object implements self::Aoo {
+class NooVoid extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::NooVoid
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.expect b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.expect
index e72e454b225..6bb2ecb935d 100644
--- a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -164,7 +164,7 @@ class Boo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Coo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Coo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -184,7 +184,7 @@ class Eoo extends core::Object implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo {
+abstract class _Foo&Boo&Aoo = self::Boo with self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -199,7 +199,7 @@ class Goo = self::Boo with self::Aoo {
     : super self::Boo::•()
     ;
 }
-abstract class _Hoo&Object&Aoo = core::Object with self::Aoo {
+abstract class _Hoo&Object&Aoo = core::Object with self::Aoo /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_Hoo&Object&Aoo
     : super core::Object::•()
     ;
@@ -214,7 +214,7 @@ class Ioo = core::Object with self::Aoo implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Joo&Boo&Never extends self::Boo {
+abstract class _Joo&Boo&Never extends self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Joo&Boo&Never
     : super self::Boo::•()
     ;
@@ -234,31 +234,31 @@ class Loo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Moo1 extends self::Aoo implements self::Boo {
+abstract class Moo1 extends self::Aoo implements self::Boo /*isMixinDeclaration*/  {
 }
-abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo {
+abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo2&Aoo&Boo
     : super core::Object::•()
     ;
 }
-abstract class Moo2 extends self::_Moo2&Aoo&Boo {
+abstract class Moo2 extends self::_Moo2&Aoo&Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo3 extends core::Object implements self::Aoo, self::Boo {
+abstract class Moo3 extends core::Object implements self::Aoo, self::Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo4 extends self::Aoo {
+abstract class Moo4 extends self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo {
+abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo5&Aoo&Never
     : super core::Object::•()
     ;
 }
-abstract class Moo5 extends self::_Moo5&Aoo&Never {
+abstract class Moo5 extends self::_Moo5&Aoo&Never /*isMixinDeclaration*/  {
 }
-abstract class Moo6 extends core::Object {
+abstract class Moo6 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class Moo7 extends core::Object implements self::Aoo {
+abstract class Moo7 extends core::Object implements self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class Moo8 extends core::Object {
+abstract class Moo8 extends core::Object /*isMixinDeclaration*/  {
 }
 class Noo = core::Object with self::Aoo {
   synthetic constructor •() → self::Noo
diff --git a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.transformed.expect
index dffeb69b6e9..470a8e7ee98 100644
--- a/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/forbidden_supers.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -164,7 +164,7 @@ class Boo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Coo&Boo&Aoo extends self::Boo implements self::Aoo {
+abstract class _Coo&Boo&Aoo extends self::Boo implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Coo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -184,7 +184,7 @@ class Eoo extends core::Object implements self::Boo {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&Boo&Aoo extends self::Boo implements self::Aoo {
+abstract class _Foo&Boo&Aoo extends self::Boo implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Foo&Boo&Aoo
     : super self::Boo::•()
     ;
@@ -194,12 +194,12 @@ class Foo extends self::_Foo&Boo&Aoo {
     : super self::_Foo&Boo&Aoo::•()
     ;
 }
-class Goo extends self::Boo implements self::Aoo {
+class Goo extends self::Boo implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Goo
     : super self::Boo::•()
     ;
 }
-abstract class _Hoo&Object&Aoo extends core::Object implements self::Aoo {
+abstract class _Hoo&Object&Aoo extends core::Object implements self::Aoo /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_Hoo&Object&Aoo
     : super core::Object::•()
     ;
@@ -209,12 +209,12 @@ class Hoo extends self::_Hoo&Object&Aoo implements self::Boo {
     : super self::_Hoo&Object&Aoo::•()
     ;
 }
-class Ioo extends core::Object implements self::Boo, self::Aoo {
+class Ioo extends core::Object implements self::Boo, self::Aoo /*isEliminatedMixin*/  {
   const synthetic constructor •() → self::Ioo
     : super core::Object::•()
     ;
 }
-abstract class _Joo&Boo&Never extends self::Boo {
+abstract class _Joo&Boo&Never extends self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Joo&Boo&Never
     : super self::Boo::•()
     ;
@@ -234,43 +234,43 @@ class Loo extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class Moo1 extends self::Aoo implements self::Boo {
+abstract class Moo1 extends self::Aoo implements self::Boo /*isMixinDeclaration*/  {
 }
-abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo {
+abstract class _Moo2&Aoo&Boo extends core::Object implements self::Aoo, self::Boo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo2&Aoo&Boo
     : super core::Object::•()
     ;
 }
-abstract class Moo2 extends self::_Moo2&Aoo&Boo {
+abstract class Moo2 extends self::_Moo2&Aoo&Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo3 extends core::Object implements self::Aoo, self::Boo {
+abstract class Moo3 extends core::Object implements self::Aoo, self::Boo /*isMixinDeclaration*/  {
 }
-abstract class Moo4 extends self::Aoo {
+abstract class Moo4 extends self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo {
+abstract class _Moo5&Aoo&Never extends core::Object implements self::Aoo /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Moo5&Aoo&Never
     : super core::Object::•()
     ;
 }
-abstract class Moo5 extends self::_Moo5&Aoo&Never {
+abstract class Moo5 extends self::_Moo5&Aoo&Never /*isMixinDeclaration*/  {
 }
-abstract class Moo6 extends core::Object {
+abstract class Moo6 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class Moo7 extends core::Object implements self::Aoo {
+abstract class Moo7 extends core::Object implements self::Aoo /*isMixinDeclaration*/  {
 }
-abstract class Moo8 extends core::Object {
+abstract class Moo8 extends core::Object /*isMixinDeclaration*/  {
 }
-class Noo extends core::Object implements self::Aoo {
+class Noo extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::Noo
     : super core::Object::•()
     ;
 }
-class NooDynamic extends core::Object implements self::Aoo {
+class NooDynamic extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::NooDynamic
     : super core::Object::•()
     ;
 }
-class NooVoid extends core::Object implements self::Aoo {
+class NooVoid extends core::Object implements self::Aoo /*isEliminatedMixin*/  {
   synthetic constructor •() → self::NooVoid
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/forin.dart.outline.expect b/pkg/front_end/testcases/nnbd/forin.dart.outline.expect
index 33cd4d6ce4d..6232118e55e 100644
--- a/pkg/front_end/testcases/nnbd/forin.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/forin.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/forin.dart.strong.expect b/pkg/front_end/testcases/nnbd/forin.dart.strong.expect
index 0f795fe5b9b..d6e63245333 100644
--- a/pkg/front_end/testcases/nnbd/forin.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/forin.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/forin.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/forin.dart.strong.transformed.expect
index ac3b55d9ec7..b65a75cc6d8 100644
--- a/pkg/front_end/testcases/nnbd/forin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/forin.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/forin.dart.weak.expect b/pkg/front_end/testcases/nnbd/forin.dart.weak.expect
index 7a50a154392..36438f5430c 100644
--- a/pkg/front_end/testcases/nnbd/forin.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/forin.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/forin.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/forin.dart.weak.transformed.expect
index 39aa91b301a..d263365f5c6 100644
--- a/pkg/front_end/testcases/nnbd/forin.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/forin.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/function_types.dart.outline.expect b/pkg/front_end/testcases/nnbd/function_types.dart.outline.expect
index 56f50791f5f..39a0f40d085 100644
--- a/pkg/front_end/testcases/nnbd/function_types.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/function_types.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/function_types.dart.strong.expect b/pkg/front_end/testcases/nnbd/function_types.dart.strong.expect
index 75317809439..8edcc0ddb2b 100644
--- a/pkg/front_end/testcases/nnbd/function_types.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/function_types.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/function_types.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/function_types.dart.strong.transformed.expect
index 75317809439..8edcc0ddb2b 100644
--- a/pkg/front_end/testcases/nnbd/function_types.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/function_types.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/function_types.dart.weak.expect b/pkg/front_end/testcases/nnbd/function_types.dart.weak.expect
index 75317809439..8edcc0ddb2b 100644
--- a/pkg/front_end/testcases/nnbd/function_types.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/function_types.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/function_types.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/function_types.dart.weak.transformed.expect
index 75317809439..8edcc0ddb2b 100644
--- a/pkg/front_end/testcases/nnbd/function_types.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/function_types.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/generic_override.dart.outline.expect b/pkg/front_end/testcases/nnbd/generic_override.dart.outline.expect
index acb760927d1..0221dc88e53 100644
--- a/pkg/front_end/testcases/nnbd/generic_override.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/generic_override.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/generic_override.dart.strong.expect b/pkg/front_end/testcases/nnbd/generic_override.dart.strong.expect
index dfb0fb24d55..be101f61086 100644
--- a/pkg/front_end/testcases/nnbd/generic_override.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/generic_override.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/generic_override.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/generic_override.dart.strong.transformed.expect
index dfb0fb24d55..be101f61086 100644
--- a/pkg/front_end/testcases/nnbd/generic_override.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/generic_override.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/generic_override.dart.weak.expect b/pkg/front_end/testcases/nnbd/generic_override.dart.weak.expect
index dfb0fb24d55..be101f61086 100644
--- a/pkg/front_end/testcases/nnbd/generic_override.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/generic_override.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/generic_override.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/generic_override.dart.weak.transformed.expect
index dfb0fb24d55..be101f61086 100644
--- a/pkg/front_end/testcases/nnbd/generic_override.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/generic_override.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.outline.expect
index 4706d9d8378..8ab794b59f8 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
@@ -9,7 +9,7 @@ static method reify<T extends core::Object? = dynamic>(self::reify::T% arg) →
 static method main() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 import self as self2;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.expect
index 840dfcae818..ff3f27295aa 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_in_lib.dart" as inf;
@@ -17,7 +17,7 @@ static method main() → dynamic {
   core::print(self::reify<() → inf::Foo>(z));
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inf;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.transformed.expect
index 840dfcae818..ff3f27295aa 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_in_lib.dart" as inf;
@@ -17,7 +17,7 @@ static method main() → dynamic {
   core::print(self::reify<() → inf::Foo>(z));
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inf;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.expect
index 840dfcae818..ff3f27295aa 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_in_lib.dart" as inf;
@@ -17,7 +17,7 @@ static method main() → dynamic {
   core::print(self::reify<() → inf::Foo>(z));
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inf;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.transformed.expect
index 840dfcae818..ff3f27295aa 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_in.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_in_lib.dart" as inf;
@@ -17,7 +17,7 @@ static method main() → dynamic {
   core::print(self::reify<() → inf::Foo>(z));
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inf;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.outline.expect
index d160bcf22d9..ffc325398c5 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.expect
index b217fb18000..99987735281 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_out_lib.dart" as inf;
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.transformed.expect
index b217fb18000..99987735281 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_out_lib.dart" as inf;
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.expect
index b217fb18000..99987735281 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_out_lib.dart" as inf;
diff --git a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.transformed.expect
index b217fb18000..99987735281 100644
--- a/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_from_opt_out.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "infer_from_opt_out_lib.dart" as inf;
diff --git a/pkg/front_end/testcases/nnbd/infer_if_null.dart.outline.expect b/pkg/front_end/testcases/nnbd/infer_if_null.dart.outline.expect
index b4b97985155..1c9be609157 100644
--- a/pkg/front_end/testcases/nnbd/infer_if_null.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/infer_if_null.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.expect b/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.expect
index 37919d9dc5f..ac0794c3a34 100644
--- a/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.transformed.expect
index 37919d9dc5f..ac0794c3a34 100644
--- a/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_if_null.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.expect b/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.expect
index 37919d9dc5f..ac0794c3a34 100644
--- a/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.transformed.expect
index 37919d9dc5f..ac0794c3a34 100644
--- a/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/infer_if_null.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.outline.expect
index 990cd89d256..039586e00b0 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.outline.expect
@@ -74,7 +74,7 @@ class LegacyClass6b<T extends core::Object* = dynamic> extends self::LegacyClass
     ;
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inh;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.strong.expect
index b0151bf1fbc..8edb63178e1 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.strong.expect
@@ -86,7 +86,7 @@ class LegacyClass6b<T extends core::Object* = dynamic> extends self::LegacyClass
     ;
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inh;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.weak.expect
index b0151bf1fbc..8edb63178e1 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_in.dart.weak.expect
@@ -86,7 +86,7 @@ class LegacyClass6b<T extends core::Object* = dynamic> extends self::LegacyClass
     ;
 }
 
-library;
+library /*isNonNullableByDefault*/;
 import self as inh;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.outline.expect
index bc326caab3f..dafa5988688 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "inheritance_from_opt_out_lib.dart" as inh;
 import "dart:core" as core;
@@ -72,7 +72,7 @@ class LegacyClass5<T extends core::Object* = dynamic> extends inh::LegacyClass3<
   synthetic constructor •() → inh::LegacyClass5<inh::LegacyClass5::T*>*
     ;
 }
-abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> {
+abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass6&Object&LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
@@ -85,7 +85,7 @@ class LegacyClass7<T extends core::Object* = dynamic> extends inh::LegacyClass3<
   synthetic constructor •() → inh::LegacyClass7<inh::LegacyClass7::T*>*
     ;
 }
-abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> {
+abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass8&Object&LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.expect
index 3c23fa9ed07..8706c9514fa 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "inheritance_from_opt_out_lib.dart" as inh;
 import "dart:core" as core;
@@ -86,7 +86,7 @@ class LegacyClass5<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> {
+abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass6&Object&LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
@@ -101,7 +101,7 @@ class LegacyClass7<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> {
+abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass8&Object&LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.transformed.expect
index 7104872fe42..187a2849a54 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "inheritance_from_opt_out_lib.dart" as inh;
 import "dart:core" as core;
@@ -86,7 +86,7 @@ class LegacyClass5<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> {
+abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass6&Object&LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
@@ -101,7 +101,7 @@ class LegacyClass7<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> {
+abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass8&Object&LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.expect
index 3c23fa9ed07..8706c9514fa 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "inheritance_from_opt_out_lib.dart" as inh;
 import "dart:core" as core;
@@ -86,7 +86,7 @@ class LegacyClass5<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> {
+abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass6&Object&LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
@@ -101,7 +101,7 @@ class LegacyClass7<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> {
+abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> = core::Object with inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> /*isAnonymousMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass8&Object&LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.transformed.expect
index 7104872fe42..187a2849a54 100644
--- a/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/inheritance_from_opt_out.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "inheritance_from_opt_out_lib.dart" as inh;
 import "dart:core" as core;
@@ -86,7 +86,7 @@ class LegacyClass5<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> {
+abstract class _LegacyClass6&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass6&Object&LegacyClass3<inh::_LegacyClass6&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
@@ -101,7 +101,7 @@ class LegacyClass7<T extends core::Object* = dynamic> extends inh::LegacyClass3<
     : super inh::LegacyClass3::•()
     ;
 }
-abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> {
+abstract class _LegacyClass8&Object&LegacyClass3<T extends core::Object* = dynamic> extends core::Object implements inh::LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*> /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → inh::_LegacyClass8&Object&LegacyClass3<inh::_LegacyClass8&Object&LegacyClass3::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/intersection_types.dart.outline.expect b/pkg/front_end/testcases/nnbd/intersection_types.dart.outline.expect
index d27719dd2c9..2359ed42d9b 100644
--- a/pkg/front_end/testcases/nnbd/intersection_types.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/intersection_types.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.expect b/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.expect
index 977e5683506..05572eed995 100644
--- a/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.transformed.expect
index 977e5683506..05572eed995 100644
--- a/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/intersection_types.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.expect b/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.expect
index 977e5683506..05572eed995 100644
--- a/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.transformed.expect
index 977e5683506..05572eed995 100644
--- a/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/intersection_types.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39659.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue39659.dart.outline.expect
index 896fae33574..e9150e272ed 100644
--- a/pkg/front_end/testcases/nnbd/issue39659.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue39659.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39659.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue39659.dart.strong.expect
index 10cdb88f501..910ce4fd6e7 100644
--- a/pkg/front_end/testcases/nnbd/issue39659.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue39659.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue39659.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue39659.dart.strong.transformed.expect
index 10cdb88f501..910ce4fd6e7 100644
--- a/pkg/front_end/testcases/nnbd/issue39659.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue39659.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue39659.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue39659.dart.weak.expect
index 5d169f79e2d..05797294b29 100644
--- a/pkg/front_end/testcases/nnbd/issue39659.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue39659.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue39659.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue39659.dart.weak.transformed.expect
index 5d169f79e2d..05797294b29 100644
--- a/pkg/front_end/testcases/nnbd/issue39659.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue39659.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue39822.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue39822.dart.outline.expect
index bbacb296723..bc24ff1540e 100644
--- a/pkg/front_end/testcases/nnbd/issue39822.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue39822.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39822.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue39822.dart.strong.expect
index a838ef12d6e..14a65982f9c 100644
--- a/pkg/front_end/testcases/nnbd/issue39822.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue39822.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39822.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue39822.dart.strong.transformed.expect
index a838ef12d6e..14a65982f9c 100644
--- a/pkg/front_end/testcases/nnbd/issue39822.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue39822.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39822.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue39822.dart.weak.expect
index a838ef12d6e..14a65982f9c 100644
--- a/pkg/front_end/testcases/nnbd/issue39822.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue39822.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue39822.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue39822.dart.weak.transformed.expect
index a838ef12d6e..14a65982f9c 100644
--- a/pkg/front_end/testcases/nnbd/issue39822.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue39822.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue40093.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue40093.dart.outline.expect
index 755fbeeca90..0606425ea42 100644
--- a/pkg/front_end/testcases/nnbd/issue40093.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue40093.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method error() → dynamic
diff --git a/pkg/front_end/testcases/nnbd/issue40093.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue40093.dart.strong.expect
index 2d29b2271c7..44e9546bf98 100644
--- a/pkg/front_end/testcases/nnbd/issue40093.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue40093.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue40093.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue40093.dart.strong.transformed.expect
index e732a3697df..83177bee902 100644
--- a/pkg/front_end/testcases/nnbd/issue40093.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue40093.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue40093.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue40093.dart.weak.expect
index 2d29b2271c7..44e9546bf98 100644
--- a/pkg/front_end/testcases/nnbd/issue40093.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue40093.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue40093.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue40093.dart.weak.transformed.expect
index e732a3697df..83177bee902 100644
--- a/pkg/front_end/testcases/nnbd/issue40093.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue40093.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue40134.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue40134.dart.outline.expect
index 4da80853ada..f26dd6e6a4f 100644
--- a/pkg/front_end/testcases/nnbd/issue40134.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue40134.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue40134.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue40134.dart.strong.expect
index e1c88bef9c1..0389f74beb0 100644
--- a/pkg/front_end/testcases/nnbd/issue40134.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue40134.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue40134.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue40134.dart.strong.transformed.expect
index e1c88bef9c1..0389f74beb0 100644
--- a/pkg/front_end/testcases/nnbd/issue40134.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue40134.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue40134.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue40134.dart.weak.expect
index e1c88bef9c1..0389f74beb0 100644
--- a/pkg/front_end/testcases/nnbd/issue40134.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue40134.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue40134.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue40134.dart.weak.transformed.expect
index e1c88bef9c1..0389f74beb0 100644
--- a/pkg/front_end/testcases/nnbd/issue40134.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue40134.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue_39286.dart.outline.expect
index 28744137d3f..5e60610fab2 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.expect
index ae125e8d8d2..ac11cde0b0c 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.transformed.expect
index ae125e8d8d2..ac11cde0b0c 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.expect
index ae125e8d8d2..ac11cde0b0c 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.transformed.expect
index ae125e8d8d2..ac11cde0b0c 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.outline.expect
index 8872e99a03e..1a9d471a83e 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.expect
index 4f72c3cef4f..e8d7ee9b2ec 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.transformed.expect
index 4f72c3cef4f..e8d7ee9b2ec 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.expect
index 4f72c3cef4f..e8d7ee9b2ec 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.transformed.expect
index 4f72c3cef4f..e8d7ee9b2ec 100644
--- a/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/issue_39286_2.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/late.dart.outline.expect b/pkg/front_end/testcases/nnbd/late.dart.outline.expect
index 88ea1d53752..afcd786a04f 100644
--- a/pkg/front_end/testcases/nnbd/late.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/late.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/late.dart.strong.expect b/pkg/front_end/testcases/nnbd/late.dart.strong.expect
index 854f872c396..aa6f48bce5b 100644
--- a/pkg/front_end/testcases/nnbd/late.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/late.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/late.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/late.dart.strong.transformed.expect
index 854f872c396..aa6f48bce5b 100644
--- a/pkg/front_end/testcases/nnbd/late.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/late.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/late.dart.weak.expect b/pkg/front_end/testcases/nnbd/late.dart.weak.expect
index 854f872c396..aa6f48bce5b 100644
--- a/pkg/front_end/testcases/nnbd/late.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/late.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/late.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/late.dart.weak.transformed.expect
index 854f872c396..aa6f48bce5b 100644
--- a/pkg/front_end/testcases/nnbd/late.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/late.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/later.dart.outline.expect b/pkg/front_end/testcases/nnbd/later.dart.outline.expect
index c3b75442a91..6e60e3f8e83 100644
--- a/pkg/front_end/testcases/nnbd/later.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/later.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -23,7 +23,7 @@ class A extends core::Object {
   method foo(core::int x) → dynamic
     ;
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   late final field core::int x = 42;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/later.dart.strong.expect b/pkg/front_end/testcases/nnbd/later.dart.strong.expect
index e96accc9c8e..dc130bf0568 100644
--- a/pkg/front_end/testcases/nnbd/later.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/later.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -74,7 +74,7 @@ class A extends core::Object {
     ;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   late final field core::int x = 42;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/later.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/later.dart.strong.transformed.expect
index 982ee0cd17b..b55281618c4 100644
--- a/pkg/front_end/testcases/nnbd/later.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/later.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -75,7 +75,7 @@ class A extends core::Object {
     ;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   late final field core::int x = 42;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/later.dart.weak.expect b/pkg/front_end/testcases/nnbd/later.dart.weak.expect
index 09e7b68d179..ec038189213 100644
--- a/pkg/front_end/testcases/nnbd/later.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/later.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -74,7 +74,7 @@ class A extends core::Object {
     ;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   late final field core::int x = 42;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/later.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/later.dart.weak.transformed.expect
index c96bcbb24cd..92d0bcf55cd 100644
--- a/pkg/front_end/testcases/nnbd/later.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/later.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -75,7 +75,7 @@ class A extends core::Object {
     ;
   method foo(core::int x) → dynamic {}
 }
-class B extends core::Object {
+class B extends core::Object /*hasConstConstructor*/  {
   late final field core::int x = 42;
   const constructor •() → self::B
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.outline.expect b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.outline.expect
index 5fe8d315090..5b45a7e5ca1 100644
--- a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.expect b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.expect
index 635fce344d8..b8f0b540e63 100644
--- a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.transformed.expect
index 635fce344d8..b8f0b540e63 100644
--- a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.expect b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.expect
index 635fce344d8..b8f0b540e63 100644
--- a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.transformed.expect
index 635fce344d8..b8f0b540e63 100644
--- a/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/lhs_of_if_null.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/list_constructor.dart.outline.expect b/pkg/front_end/testcases/nnbd/list_constructor.dart.outline.expect
index 00f17da04bc..b62277018de 100644
--- a/pkg/front_end/testcases/nnbd/list_constructor.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/list_constructor.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.expect b/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.expect
index 788fdeb628f..5cc723ca479 100644
--- a/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.transformed.expect
index 64a625b6f9d..78ee25b65c6 100644
--- a/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/list_constructor.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.expect b/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.expect
index e72bdc93f9f..4b2756e5111 100644
--- a/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.transformed.expect
index eda551156b2..80f0ed3d0d9 100644
--- a/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/list_constructor.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.outline.expect
index dcd675fe3b3..331438b0153 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.outline.expect
@@ -75,7 +75,7 @@ class LegacyClass extends mem::Class implements mem::Interface {
 static method main() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 import self as mem;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.expect
index c6a3171d485..a926f8bf493 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.expect
@@ -71,7 +71,7 @@ class LegacyClass extends mem::Class implements mem::Interface {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as mem;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.transformed.expect
index c6a3171d485..a926f8bf493 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.strong.transformed.expect
@@ -71,7 +71,7 @@ class LegacyClass extends mem::Class implements mem::Interface {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as mem;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.expect
index c6a3171d485..a926f8bf493 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.expect
@@ -71,7 +71,7 @@ class LegacyClass extends mem::Class implements mem::Interface {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as mem;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.transformed.expect
index c6a3171d485..a926f8bf493 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_in.dart.weak.transformed.expect
@@ -71,7 +71,7 @@ class LegacyClass extends mem::Class implements mem::Interface {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as mem;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.outline.expect
index 50ad3f4ea73..bf466c55fed 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.outline.expect
@@ -1,4 +1,4 @@
-library main;
+library main /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "member_inheritance_from_opt_out_lib.dart" as opt;
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.expect
index 20453f0949e..85e1534b2c8 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.expect
@@ -1,4 +1,4 @@
-library main;
+library main /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "member_inheritance_from_opt_out_lib.dart" as opt;
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.transformed.expect
index 20453f0949e..85e1534b2c8 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library main;
+library main /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "member_inheritance_from_opt_out_lib.dart" as opt;
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.expect
index 20453f0949e..85e1534b2c8 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.expect
@@ -1,4 +1,4 @@
-library main;
+library main /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "member_inheritance_from_opt_out_lib.dart" as opt;
diff --git a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.transformed.expect
index 20453f0949e..85e1534b2c8 100644
--- a/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/member_inheritance_from_opt_out.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library main;
+library main /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 import "member_inheritance_from_opt_out_lib.dart" as opt;
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.outline.expect
index a1fe8bfe28a..32b8bce221a 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.strong.expect
index 123a8217dcd..02f979f6d65 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.weak.expect
index 123a8217dcd..02f979f6d65 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_in.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.outline.expect
index 5dc40b08169..346613a9aa5 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.outline.expect
@@ -80,7 +80,7 @@ static field core::String* legacyVar;
 static method testOptOut() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.strong.expect
index 2b26e9b7952..828c85b6e3b 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.strong.expect
@@ -125,7 +125,7 @@ static method testOptOut() → dynamic {
               ^" in mes::nonNullableVar as{TypeError} core::String*;
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.weak.expect
index 2b26e9b7952..828c85b6e3b 100644
--- a/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/messages_with_types_opt_out.dart.weak.expect
@@ -125,7 +125,7 @@ static method testOptOut() → dynamic {
               ^" in mes::nonNullableVar as{TypeError} core::String*;
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.outline.expect b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.outline.expect
index 18f2365ca76..e04c31a9272 100644
--- a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.expect b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.expect
index 46eca1c8a36..cf64382b1c6 100644
--- a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.transformed.expect
index 46eca1c8a36..cf64382b1c6 100644
--- a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.expect b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.expect
index de95e8d8373..0a032ba6d9c 100644
--- a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.transformed.expect
index de95e8d8373..0a032ba6d9c 100644
--- a/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/missing_required_named_parameter.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart
new file mode 100644
index 00000000000..1de618fe54c
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart
@@ -0,0 +1,13 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.6
+
+import 'mixin_from_opt_in_lib.dart';
+
+class Class extends Object with Mixin {}
+
+main() {
+  print(new Class().method(null));
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.outline.expect
new file mode 100644
index 00000000000..36ff7da6b3f
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.outline.expect
@@ -0,0 +1,30 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_in_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_in_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin*
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class*
+    ;
+  abstract member-signature method method(core::int* i) → core::int*;
+}
+static method main() → dynamic
+  ;
+
+library /*isNonNullableByDefault*/;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin
+    ;
+  method method(core::int? i) → core::int
+    ;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.expect
new file mode 100644
index 00000000000..f71915b7c47
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.expect
@@ -0,0 +1,33 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_in_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_in_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin*
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class*
+    : super self::_Class&Object&Mixin::•()
+    ;
+  abstract member-signature method method(core::int* i) → core::int*;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{self::Class::method}(null));
+}
+
+library /*isNonNullableByDefault*/;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.transformed.expect
new file mode 100644
index 00000000000..7dd0788da38
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.strong.transformed.expect
@@ -0,0 +1,35 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_in_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_in_lib.dart";
+
+abstract class _Class&Object&Mixin extends core::Object implements mix::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin*
+    : super core::Object::•()
+    ;
+  method /*isNonNullableByDefault, from org-dartlang-testcase:///mixin_from_opt_in_lib.dart */ method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class*
+    : super self::_Class&Object&Mixin::•()
+    ;
+  abstract member-signature method method(core::int* i) → core::int*;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{self::Class::method}(null));
+}
+
+library /*isNonNullableByDefault*/;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t2 = i in #t2.{core::num::==}(null) ?{core::int} 0 : #t2{core::int};
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.expect
new file mode 100644
index 00000000000..f71915b7c47
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.expect
@@ -0,0 +1,33 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_in_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_in_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin*
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class*
+    : super self::_Class&Object&Mixin::•()
+    ;
+  abstract member-signature method method(core::int* i) → core::int*;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{self::Class::method}(null));
+}
+
+library /*isNonNullableByDefault*/;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.transformed.expect
new file mode 100644
index 00000000000..7dd0788da38
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in.dart.weak.transformed.expect
@@ -0,0 +1,35 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_in_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_in_lib.dart";
+
+abstract class _Class&Object&Mixin extends core::Object implements mix::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin*
+    : super core::Object::•()
+    ;
+  method /*isNonNullableByDefault, from org-dartlang-testcase:///mixin_from_opt_in_lib.dart */ method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class*
+    : super self::_Class&Object&Mixin::•()
+    ;
+  abstract member-signature method method(core::int* i) → core::int*;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{self::Class::method}(null));
+}
+
+library /*isNonNullableByDefault*/;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t2 = i in #t2.{core::num::==}(null) ?{core::int} 0 : #t2{core::int};
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_in_lib.dart b/pkg/front_end/testcases/nnbd/mixin_from_opt_in_lib.dart
new file mode 100644
index 00000000000..5159fb1dca1
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_in_lib.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class Mixin {
+  int method(int? i) => i ?? 0;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart
new file mode 100644
index 00000000000..b5433d7a33c
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart
@@ -0,0 +1,11 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'mixin_from_opt_out_lib.dart';
+
+class Class extends Object with Mixin {}
+
+main() {
+  print(new Class().method(null));
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.outline.expect
new file mode 100644
index 00000000000..7e6b375cf28
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.outline.expect
@@ -0,0 +1,29 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_out_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_out_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class
+    ;
+}
+static method main() → dynamic
+  ;
+
+library;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin*
+    ;
+  method method(core::int* i) → core::int*
+    ;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.expect
new file mode 100644
index 00000000000..342e2d1b928
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.expect
@@ -0,0 +1,32 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_out_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_out_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class
+    : super self::_Class&Object&Mixin::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{mix::Mixin::method}(null));
+}
+
+library;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin*
+    : super core::Object::•()
+    ;
+  method method(core::int* i) → core::int*
+    return let final core::int* #t1 = i in #t1.{core::num::==}(null) ?{core::int*} 0 : #t1;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.transformed.expect
new file mode 100644
index 00000000000..8106b0bcf3a
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.strong.transformed.expect
@@ -0,0 +1,34 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_out_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_out_lib.dart";
+
+abstract class _Class&Object&Mixin extends core::Object implements mix::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin
+    : super core::Object::•()
+    ;
+  method /*isNullableByDefault, from org-dartlang-testcase:///mixin_from_opt_out_lib.dart */ method(core::int* i) → core::int*
+    return let final core::int* #t1 = i in #t1.{core::num::==}(null) ?{core::int*} 0 : #t1;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class
+    : super self::_Class&Object&Mixin::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{mix::Mixin::method}(null));
+}
+
+library;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin*
+    : super core::Object::•()
+    ;
+  method method(core::int* i) → core::int*
+    return let final core::int* #t2 = i in #t2.{core::num::==}(null) ?{core::int*} 0 : #t2;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.expect
new file mode 100644
index 00000000000..342e2d1b928
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.expect
@@ -0,0 +1,32 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_out_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_out_lib.dart";
+
+abstract class _Class&Object&Mixin = core::Object with mix::Mixin /*isAnonymousMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin
+    : super core::Object::•()
+    ;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class
+    : super self::_Class&Object&Mixin::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{mix::Mixin::method}(null));
+}
+
+library;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin*
+    : super core::Object::•()
+    ;
+  method method(core::int* i) → core::int*
+    return let final core::int* #t1 = i in #t1.{core::num::==}(null) ?{core::int*} 0 : #t1;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.transformed.expect
new file mode 100644
index 00000000000..8106b0bcf3a
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out.dart.weak.transformed.expect
@@ -0,0 +1,34 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "mixin_from_opt_out_lib.dart" as mix;
+
+import "org-dartlang-testcase:///mixin_from_opt_out_lib.dart";
+
+abstract class _Class&Object&Mixin extends core::Object implements mix::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
+  const synthetic constructor •() → self::_Class&Object&Mixin
+    : super core::Object::•()
+    ;
+  method /*isNullableByDefault, from org-dartlang-testcase:///mixin_from_opt_out_lib.dart */ method(core::int* i) → core::int*
+    return let final core::int* #t1 = i in #t1.{core::num::==}(null) ?{core::int*} 0 : #t1;
+}
+class Class extends self::_Class&Object&Mixin {
+  synthetic constructor •() → self::Class
+    : super self::_Class&Object&Mixin::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::Class::•().{mix::Mixin::method}(null));
+}
+
+library;
+import self as mix;
+import "dart:core" as core;
+
+class Mixin extends core::Object {
+  synthetic constructor •() → mix::Mixin*
+    : super core::Object::•()
+    ;
+  method method(core::int* i) → core::int*
+    return let final core::int* #t2 = i in #t2.{core::num::==}(null) ?{core::int*} 0 : #t2;
+}
diff --git a/pkg/front_end/testcases/nnbd/mixin_from_opt_out_lib.dart b/pkg/front_end/testcases/nnbd/mixin_from_opt_out_lib.dart
new file mode 100644
index 00000000000..fd695dec2d3
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/mixin_from_opt_out_lib.dart
@@ -0,0 +1,9 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.6
+
+class Mixin {
+  int method(int i) => i ?? 0;
+}
diff --git a/pkg/front_end/testcases/nnbd/never_receiver.dart.outline.expect b/pkg/front_end/testcases/nnbd/never_receiver.dart.outline.expect
index 95bf11856f8..fec2e44fe78 100644
--- a/pkg/front_end/testcases/nnbd/never_receiver.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/never_receiver.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo(Neverx, Never? y) → dynamic
diff --git a/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.expect b/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.expect
index 3ec8d1f49db..feeca8080f0 100644
--- a/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.transformed.expect
index 3ec8d1f49db..feeca8080f0 100644
--- a/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/never_receiver.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.expect b/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.expect
index d147c4edb58..6c9dc2043ed 100644
--- a/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.transformed.expect
index d147c4edb58..6c9dc2043ed 100644
--- a/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/never_receiver.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.outline.expect b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.outline.expect
index 56810f637b3..057a76fd88e 100644
--- a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -37,11 +37,11 @@ class B<X extends core::Object? = core::Object?, Y extends core::Object = core::
   constructor bar(self::B::X% fieldOfB, self::B::Y fieldOfB2) → self::B<self::B::X%, self::B::Y>
     ;
 }
-abstract class M extends core::Object {
+abstract class M extends core::Object /*isMixinDeclaration*/  {
   static field core::int staticFieldOfM;
   field core::int fieldOfM;
 }
-abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   generic-covariant-impl field self::N::X% fieldOfN;
   generic-covariant-impl field self::N::Y fieldOfN2;
 }
@@ -64,7 +64,7 @@ class C<X extends core::Object? = core::Object?, Y extends core::Object = core::
   constructor bar(core::int fieldOfC10) → self::C<self::C::X%, self::C::Y>
     ;
 }
-abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   static field core::int? staticFieldOfL;
   static field core::int staticFieldOfLInitialized;
   generic-covariant-impl field self::L::X? fieldOfL;
diff --git a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.expect b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.expect
index 90d9ea57a76..bd5dcc79a12 100644
--- a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -66,11 +66,11 @@ class B<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::B::fieldOfB = fieldOfB, self::B::fieldOfB2 = fieldOfB2, super core::Object::•()
     ;
 }
-abstract class M extends core::Object {
+abstract class M extends core::Object /*isMixinDeclaration*/  {
   static field core::int staticFieldOfM = null;
   field core::int fieldOfM = null;
 }
-abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   generic-covariant-impl field self::N::X% fieldOfN = null;
   generic-covariant-impl field self::N::Y fieldOfN2 = null;
 }
@@ -95,7 +95,7 @@ class C<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::C::fieldOfC10 = fieldOfC10, super core::Object::•()
     ;
 }
-abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   static field core::int? staticFieldOfL = null;
   static field core::int staticFieldOfLInitialized = 42;
   generic-covariant-impl field self::L::X? fieldOfL = null;
diff --git a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.transformed.expect
index 90d9ea57a76..bd5dcc79a12 100644
--- a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -66,11 +66,11 @@ class B<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::B::fieldOfB = fieldOfB, self::B::fieldOfB2 = fieldOfB2, super core::Object::•()
     ;
 }
-abstract class M extends core::Object {
+abstract class M extends core::Object /*isMixinDeclaration*/  {
   static field core::int staticFieldOfM = null;
   field core::int fieldOfM = null;
 }
-abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   generic-covariant-impl field self::N::X% fieldOfN = null;
   generic-covariant-impl field self::N::Y fieldOfN2 = null;
 }
@@ -95,7 +95,7 @@ class C<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::C::fieldOfC10 = fieldOfC10, super core::Object::•()
     ;
 }
-abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   static field core::int? staticFieldOfL = null;
   static field core::int staticFieldOfLInitialized = 42;
   generic-covariant-impl field self::L::X? fieldOfL = null;
diff --git a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.expect b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.expect
index 29e2ddeac16..7f76fc6cecc 100644
--- a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -66,11 +66,11 @@ class B<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::B::fieldOfB = fieldOfB, self::B::fieldOfB2 = fieldOfB2, super core::Object::•()
     ;
 }
-abstract class M extends core::Object {
+abstract class M extends core::Object /*isMixinDeclaration*/  {
   static field core::int staticFieldOfM = null;
   field core::int fieldOfM = null;
 }
-abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   generic-covariant-impl field self::N::X% fieldOfN = null;
   generic-covariant-impl field self::N::Y fieldOfN2 = null;
 }
@@ -95,7 +95,7 @@ class C<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::C::fieldOfC10 = fieldOfC10, super core::Object::•()
     ;
 }
-abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   static field core::int? staticFieldOfL = null;
   static field core::int staticFieldOfLInitialized = 42;
   generic-covariant-impl field self::L::X? fieldOfL = null;
diff --git a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.transformed.expect
index 29e2ddeac16..7f76fc6cecc 100644
--- a/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/non_nullable_field_initialization.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -66,11 +66,11 @@ class B<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::B::fieldOfB = fieldOfB, self::B::fieldOfB2 = fieldOfB2, super core::Object::•()
     ;
 }
-abstract class M extends core::Object {
+abstract class M extends core::Object /*isMixinDeclaration*/  {
   static field core::int staticFieldOfM = null;
   field core::int fieldOfM = null;
 }
-abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class N<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   generic-covariant-impl field self::N::X% fieldOfN = null;
   generic-covariant-impl field self::N::Y fieldOfN2 = null;
 }
@@ -95,7 +95,7 @@ class C<X extends core::Object? = core::Object?, Y extends core::Object = core::
     : self::C::fieldOfC10 = fieldOfC10, super core::Object::•()
     ;
 }
-abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object {
+abstract class L<X extends core::Object? = core::Object?, Y extends core::Object = core::Object> extends core::Object /*isMixinDeclaration*/  {
   static field core::int? staticFieldOfL = null;
   static field core::int staticFieldOfLInitialized = 42;
   generic-covariant-impl field self::L::X? fieldOfL = null;
diff --git a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.outline.expect b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.outline.expect
index 766038c48c2..00778a819d1 100644
--- a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.outline.expect
@@ -21,7 +21,7 @@ abstract class C2 extends core::Object {
 static method main() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 import self as nsm;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.expect b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.expect
index 9bc8d0436c0..10bcb6e46df 100644
--- a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.expect
@@ -23,7 +23,7 @@ abstract class C2 extends core::Object {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as nsm;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.transformed.expect
index 9bc8d0436c0..10bcb6e46df 100644
--- a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.transformed.expect
@@ -23,7 +23,7 @@ abstract class C2 extends core::Object {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as nsm;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.expect b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.expect
index 9bc8d0436c0..10bcb6e46df 100644
--- a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.expect
@@ -23,7 +23,7 @@ abstract class C2 extends core::Object {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as nsm;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.transformed.expect
index 9bc8d0436c0..10bcb6e46df 100644
--- a/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.transformed.expect
@@ -23,7 +23,7 @@ abstract class C2 extends core::Object {
 }
 static method main() → dynamic {}
 
-library;
+library /*isNonNullableByDefault*/;
 import self as nsm;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_access.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_access.dart.outline.expect
index 42298883160..5f23d7a4d79 100644
--- a/pkg/front_end/testcases/nnbd/null_access.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_access.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_access.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_access.dart.strong.expect
index ac5f13bc290..39e0fe7d8ce 100644
--- a/pkg/front_end/testcases/nnbd/null_access.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_access.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_access.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_access.dart.strong.transformed.expect
index ac5f13bc290..39e0fe7d8ce 100644
--- a/pkg/front_end/testcases/nnbd/null_access.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_access.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_access.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_access.dart.weak.expect
index 64118187c06..bf94e0af658 100644
--- a/pkg/front_end/testcases/nnbd/null_access.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_access.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_access.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_access.dart.weak.transformed.expect
index 64118187c06..bf94e0af658 100644
--- a/pkg/front_end/testcases/nnbd/null_access.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_access.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.outline.expect
index af3d1e98512..1570628a427 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.expect
index f74ed66ebfd..267161a31c6 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.transformed.expect
index f74ed66ebfd..267161a31c6 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.expect
index f74ed66ebfd..267161a31c6 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.transformed.expect
index f74ed66ebfd..267161a31c6 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_chain.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_check.dart.outline.expect
index aa7235a1360..23ccd448b16 100644
--- a/pkg/front_end/testcases/nnbd/null_check.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_check.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_check.dart.strong.expect
index 28637dd83e3..26ca627f1c4 100644
--- a/pkg/front_end/testcases/nnbd/null_check.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_check.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_check.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_check.dart.strong.transformed.expect
index 28637dd83e3..26ca627f1c4 100644
--- a/pkg/front_end/testcases/nnbd/null_check.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_check.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_check.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_check.dart.weak.expect
index 28637dd83e3..26ca627f1c4 100644
--- a/pkg/front_end/testcases/nnbd/null_check.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_check.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_check.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_check.dart.weak.transformed.expect
index 28637dd83e3..26ca627f1c4 100644
--- a/pkg/front_end/testcases/nnbd/null_check.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_check.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_check_context.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_check_context.dart.outline.expect
index 61468b9611f..1e606c362af 100644
--- a/pkg/front_end/testcases/nnbd/null_check_context.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_check_context.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.expect
index c4bea6d4b7a..a9e189a3681 100644
--- a/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.transformed.expect
index c4bea6d4b7a..a9e189a3681 100644
--- a/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_check_context.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.expect
index c4bea6d4b7a..a9e189a3681 100644
--- a/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.transformed.expect
index c4bea6d4b7a..a9e189a3681 100644
--- a/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_check_context.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting.dart.outline.expect
index 6eb9d378ac7..307f52e2e70 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.expect
index 7f40a028b8e..4b8eb0a48e5 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.transformed.expect
index 7f40a028b8e..4b8eb0a48e5 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.expect
index 0a885800063..16671663485 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.transformed.expect
index 0a885800063..16671663485 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect
index 433ed24e134..7cc6fec749f 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect
index 60aef17df28..1e6793a07d3 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect
index 60aef17df28..1e6793a07d3 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.expect
index 60aef17df28..1e6793a07d3 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.transformed.expect
index 60aef17df28..1e6793a07d3 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.outline.expect
index 32edac15180..6e171319443 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.expect
index 93172a118ec..ad010f7f098 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.transformed.expect
index 93172a118ec..ad010f7f098 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.expect
index 0f1219791aa..559dca69ad8 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.transformed.expect
index 0f1219791aa..559dca69ad8 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_explicit_extension.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.outline.expect
index 32edac15180..6e171319443 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.expect
index 08bb2f473de..51808dbca92 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.transformed.expect
index 08bb2f473de..51808dbca92 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.expect
index 47d4d98c342..dce59316122 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.transformed.expect
index 47d4d98c342..dce59316122 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_extension.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.outline.expect
index 6b81c57b8ed..c13bf31efd4 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.expect
index 107e73d1837..111b12b7506 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.transformed.expect
index 107e73d1837..111b12b7506 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.expect
index 107e73d1837..111b12b7506 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.transformed.expect
index 107e73d1837..111b12b7506 100644
--- a/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_shorting_index.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/nullable_access.dart.outline.expect b/pkg/front_end/testcases/nnbd/nullable_access.dart.outline.expect
index 6a7422304e3..64040bcbc58 100644
--- a/pkg/front_end/testcases/nnbd/nullable_access.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_access.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
@@ -13,7 +13,7 @@ class Class extends core::Object {
   method nonNullableMethod() → self::A
     ;
 }
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.expect b/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.expect
index 509f9241f8a..969933634bf 100644
--- a/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -24,7 +24,7 @@ class Class extends core::Object {
   method nonNullableMethod() → self::A
     return this.{self::Class::nonNullableField};
 }
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.transformed.expect
index 509f9241f8a..969933634bf 100644
--- a/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_access.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -24,7 +24,7 @@ class Class extends core::Object {
   method nonNullableMethod() → self::A
     return this.{self::Class::nonNullableField};
 }
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.expect b/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.expect
index ca860c8955f..dc3992fa40c 100644
--- a/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -24,7 +24,7 @@ class Class extends core::Object {
   method nonNullableMethod() → self::A
     return this.{self::Class::nonNullableField};
 }
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.transformed.expect
index ca860c8955f..dc3992fa40c 100644
--- a/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_access.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
@@ -24,7 +24,7 @@ class Class extends core::Object {
   method nonNullableMethod() → self::A
     return this.{self::Class::nonNullableField};
 }
-class A extends core::Object {
+class A extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::A
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/nnbd/nullable_null.dart.outline.expect b/pkg/front_end/testcases/nnbd/nullable_null.dart.outline.expect
index 937afc398b9..f1b5ac6aa20 100644
--- a/pkg/front_end/testcases/nnbd/nullable_null.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_null.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.expect b/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.expect
index bf6195bab0b..a19cb5b3d3f 100644
--- a/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.transformed.expect
index bf6195bab0b..a19cb5b3d3f 100644
--- a/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_null.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.expect b/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.expect
index d3205a98415..7efdb661555 100644
--- a/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.transformed.expect
index d3205a98415..7efdb661555 100644
--- a/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_null.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_param.dart.outline.expect b/pkg/front_end/testcases/nnbd/nullable_param.dart.outline.expect
index 5309a2b68ca..24ecf42f35c 100644
--- a/pkg/front_end/testcases/nnbd/nullable_param.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_param.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.expect b/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.expect
index 3adb898ac31..9ab606911f6 100644
--- a/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.transformed.expect
index 3adb898ac31..9ab606911f6 100644
--- a/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_param.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.expect b/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.expect
index 3adb898ac31..9ab606911f6 100644
--- a/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.transformed.expect
index 3adb898ac31..9ab606911f6 100644
--- a/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_param.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.outline.expect b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.outline.expect
index 8b1efd63c95..d88e541e76b 100644
--- a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.expect b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.expect
index 4572332b2ea..a326cf278c8 100644
--- a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.transformed.expect
index 4572332b2ea..a326cf278c8 100644
--- a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.expect b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.expect
index cd79d913e44..a00b5743a90 100644
--- a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.transformed.expect
index cd79d913e44..a00b5743a90 100644
--- a/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/nullable_receiver.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/opt_out.dart.outline.expect b/pkg/front_end/testcases/nnbd/opt_out.dart.outline.expect
index b08c2be2d73..11d7a437b61 100644
--- a/pkg/front_end/testcases/nnbd/opt_out.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/opt_out.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/opt_out.dart.strong.expect b/pkg/front_end/testcases/nnbd/opt_out.dart.strong.expect
index 02ebaa2195b..fa109913ff5 100644
--- a/pkg/front_end/testcases/nnbd/opt_out.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/opt_out.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/opt_out.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/opt_out.dart.strong.transformed.expect
index 02ebaa2195b..fa109913ff5 100644
--- a/pkg/front_end/testcases/nnbd/opt_out.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/opt_out.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/opt_out.dart.weak.expect b/pkg/front_end/testcases/nnbd/opt_out.dart.weak.expect
index 02ebaa2195b..fa109913ff5 100644
--- a/pkg/front_end/testcases/nnbd/opt_out.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/opt_out.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/opt_out.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/opt_out.dart.weak.transformed.expect
index 02ebaa2195b..fa109913ff5 100644
--- a/pkg/front_end/testcases/nnbd/opt_out.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/opt_out.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
index ab6f6909b91..cae508d4fa3 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 import "dart:test";
@@ -6,7 +6,7 @@ import "dart:test";
 static method main() → dynamic
   ;
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
index 1f952a25ed7..9a4131e7558 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:test" as test;
 
@@ -8,7 +8,7 @@ static method main() → dynamic {
   test::Class? c = new test::Class::•();
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
index 1f952a25ed7..9a4131e7558 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:test" as test;
 
@@ -8,7 +8,7 @@ static method main() → dynamic {
   test::Class? c = new test::Class::•();
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
index 33e8f391e21..0faff1254ad 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:test" as test;
 
@@ -8,7 +8,7 @@ static method main() → dynamic {
   test::Class? c = new test::Class::•();
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
index 33e8f391e21..0faff1254ad 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:test" as test;
 
@@ -8,7 +8,7 @@ static method main() → dynamic {
   test::Class? c = new test::Class::•();
 }
 
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.outline.expect b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.outline.expect
index b56b2a72f06..5f5e178846e 100644
--- a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.expect b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.expect
index 0dee5415d3b..ac1c56bdf03 100644
--- a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.transformed.expect
index 0dee5415d3b..ac1c56bdf03 100644
--- a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.expect b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.expect
index ff1e157ed5e..0b34a217fbe 100644
--- a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.transformed.expect
index ff1e157ed5e..0b34a217fbe 100644
--- a/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/potentially_non_nullable_field.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required.dart.outline.expect b/pkg/front_end/testcases/nnbd/required.dart.outline.expect
index bac16043f2f..ff5e088e56d 100644
--- a/pkg/front_end/testcases/nnbd/required.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/required.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required.dart.strong.expect b/pkg/front_end/testcases/nnbd/required.dart.strong.expect
index 335594b65a7..ed0ee8ec909 100644
--- a/pkg/front_end/testcases/nnbd/required.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/required.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/required.dart.strong.transformed.expect
index 335594b65a7..ed0ee8ec909 100644
--- a/pkg/front_end/testcases/nnbd/required.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/required.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required.dart.weak.expect b/pkg/front_end/testcases/nnbd/required.dart.weak.expect
index 35a4cfc6d47..4c8f81df147 100644
--- a/pkg/front_end/testcases/nnbd/required.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/required.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/required.dart.weak.transformed.expect
index 35a4cfc6d47..4c8f81df147 100644
--- a/pkg/front_end/testcases/nnbd/required.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/required.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.outline.expect b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.outline.expect
index bfd90520af2..8dab6631170 100644
--- a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.expect b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.expect
index c706ee0536a..41566f30ebd 100644
--- a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.transformed.expect
index c706ee0536a..41566f30ebd 100644
--- a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.expect b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.expect
index f8837f91a48..8f475d6c62f 100644
--- a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.transformed.expect
index f8837f91a48..8f475d6c62f 100644
--- a/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/required_named_parameter.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/return_late.dart.outline.expect b/pkg/front_end/testcases/nnbd/return_late.dart.outline.expect
index b09c8c1c786..00f47083ef3 100644
--- a/pkg/front_end/testcases/nnbd/return_late.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/return_late.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/return_late.dart.strong.expect b/pkg/front_end/testcases/nnbd/return_late.dart.strong.expect
index 7829fc44841..66e9443aae0 100644
--- a/pkg/front_end/testcases/nnbd/return_late.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/return_late.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/return_late.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/return_late.dart.strong.transformed.expect
index 3da0607b5ce..15e637957ce 100644
--- a/pkg/front_end/testcases/nnbd/return_late.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/return_late.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/return_late.dart.weak.expect b/pkg/front_end/testcases/nnbd/return_late.dart.weak.expect
index 7829fc44841..66e9443aae0 100644
--- a/pkg/front_end/testcases/nnbd/return_late.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/return_late.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/return_late.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/return_late.dart.weak.transformed.expect
index 3da0607b5ce..15e637957ce 100644
--- a/pkg/front_end/testcases/nnbd/return_late.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/return_late.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/shorting_stop.dart.outline.expect b/pkg/front_end/testcases/nnbd/shorting_stop.dart.outline.expect
index 11c3840aad8..604aeff99a6 100644
--- a/pkg/front_end/testcases/nnbd/shorting_stop.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/shorting_stop.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.expect b/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.expect
index 69c985e9782..f35cdbd60f3 100644
--- a/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.transformed.expect
index 69c985e9782..f35cdbd60f3 100644
--- a/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/shorting_stop.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.expect b/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.expect
index 0a8d6392f4d..e32de912ad6 100644
--- a/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.transformed.expect
index 0a8d6392f4d..e32de912ad6 100644
--- a/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/shorting_stop.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/simple_never.dart.outline.expect b/pkg/front_end/testcases/nnbd/simple_never.dart.outline.expect
index a1a8eaa77ef..d0b42482c7b 100644
--- a/pkg/front_end/testcases/nnbd/simple_never.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/simple_never.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo() → Never
diff --git a/pkg/front_end/testcases/nnbd/simple_never.dart.strong.expect b/pkg/front_end/testcases/nnbd/simple_never.dart.strong.expect
index 9a621b6921a..cab8e1b4b48 100644
--- a/pkg/front_end/testcases/nnbd/simple_never.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/simple_never.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo() → Never{
diff --git a/pkg/front_end/testcases/nnbd/simple_never.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/simple_never.dart.strong.transformed.expect
index 9a621b6921a..cab8e1b4b48 100644
--- a/pkg/front_end/testcases/nnbd/simple_never.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/simple_never.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo() → Never{
diff --git a/pkg/front_end/testcases/nnbd/simple_never.dart.weak.expect b/pkg/front_end/testcases/nnbd/simple_never.dart.weak.expect
index 9a621b6921a..cab8e1b4b48 100644
--- a/pkg/front_end/testcases/nnbd/simple_never.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/simple_never.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo() → Never{
diff --git a/pkg/front_end/testcases/nnbd/simple_never.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/simple_never.dart.weak.transformed.expect
index 9a621b6921a..cab8e1b4b48 100644
--- a/pkg/front_end/testcases/nnbd/simple_never.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/simple_never.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 
 static method foo() → Never{
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.outline.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.outline.expect
index 41543538a48..6834f8262d7 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
index 39835c2b657..5f0452d677f 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
index a50498a66ee..3d6a2f4d5d7 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
index 39835c2b657..5f0452d677f 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
index a50498a66ee..3d6a2f4d5d7 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.outline.expect b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.outline.expect
index 78939a76af5..afffc1968a8 100644
--- a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.expect b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.expect
index b23b0d3bd4b..afd873e6208 100644
--- a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.transformed.expect
index b23b0d3bd4b..afd873e6208 100644
--- a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.expect b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.expect
index b23b0d3bd4b..afd873e6208 100644
--- a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.transformed.expect
index b23b0d3bd4b..afd873e6208 100644
--- a/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/substitution_in_inference.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.outline.expect b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.outline.expect
index 8f8831c2c66..bb20d27002f 100644
--- a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.expect b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.expect
index 249b918f127..19bd0ebd146 100644
--- a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.transformed.expect
index 249b918f127..19bd0ebd146 100644
--- a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.expect b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.expect
index c9f6d6a146a..2317ae79d6f 100644
--- a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.transformed.expect
index c9f6d6a146a..2317ae79d6f 100644
--- a/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/tearoff_from_nullable_receiver.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
diff --git a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.outline.expect b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.outline.expect
index c19129b979d..9c418ba3da2 100644
--- a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.outline.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.expect b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.expect
index e9e87da1dd8..4db6f6e7b5b 100644
--- a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.transformed.expect
index e9e87da1dd8..4db6f6e7b5b 100644
--- a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.strong.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.expect b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.expect
index e9e87da1dd8..4db6f6e7b5b 100644
--- a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.transformed.expect
index e9e87da1dd8..4db6f6e7b5b 100644
--- a/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/type_parameter_types.dart.weak.transformed.expect
@@ -1,4 +1,4 @@
-library;
+library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.outline.expect
index f84f93de81d..b57bf0f2c37 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.outline.expect
@@ -17,7 +17,7 @@ class B extends core::Object implements self::A {
   no-such-method-forwarder set foo(core::int* value) → void
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#foo=, 2, const <core::Type*>[], core::List::unmodifiable<dynamic>(<dynamic>[value]), core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{})));
 }
-abstract class _C&Object&B = core::Object with self::B {
+abstract class _C&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.expect
index 1f2525dbf92..1a87161a03d 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.expect
@@ -21,7 +21,7 @@ class B extends core::Object implements self::A {
   no-such-method-forwarder set foo(core::int* value) → void
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 2, #C2, core::List::unmodifiable<dynamic>(<dynamic>[value]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _C&Object&B = core::Object with self::B {
+abstract class _C&Object&B = core::Object with self::B /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_C&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.transformed.expect
index da816df4e94..2f8a597aed4 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/abstract_accessors_from_field_arent_mixed_in.dart.strong.transformed.expect
@@ -21,7 +21,7 @@ class B extends core::Object implements self::A {
   no-such-method-forwarder set foo(core::int* value) → void
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#C5, 2, #C2, core::List::unmodifiable<dynamic>(<dynamic>[value]), core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _C&Object&B extends core::Object implements self::B {
+abstract class _C&Object&B extends core::Object implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_C&Object&B*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.outline.expect
index 3adb9f506e1..4c2e89f4584 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.outline.expect
@@ -21,7 +21,7 @@ class B extends core::Object implements self::I {
   no-such-method-forwarder method foo() → dynamic
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#foo, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{}))) as{TypeError,ForDynamic} dynamic;
 }
-abstract class _C&A&B = self::A with self::B {
+abstract class _C&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.expect
index ad2597a4b2d..3c6a0582cce 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.expect
@@ -23,7 +23,7 @@ class B extends core::Object implements self::I {
   no-such-method-forwarder method foo() → dynamic
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4))) as{TypeError,ForDynamic} dynamic;
 }
-abstract class _C&A&B = self::A with self::B {
+abstract class _C&A&B = self::A with self::B /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.transformed.expect
index 23455fef767..42b6d983bcf 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/concrete_method_over_forwarder_in_mixin_application.dart.strong.transformed.expect
@@ -23,7 +23,7 @@ class B extends core::Object implements self::I {
   no-such-method-forwarder method foo() → dynamic
     return this.{self::B::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4))) as{TypeError,ForDynamic} dynamic;
 }
-abstract class _C&A&B extends self::A implements self::B {
+abstract class _C&A&B extends self::A implements self::B /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_C&A&B*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.outline.expect
index 3f045c4aaf1..edbb0ed2a98 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.outline.expect
@@ -15,7 +15,7 @@ class A extends core::Object implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::A::noSuchMethod}(new core::_InvocationMirror::_withType(#foo, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{})));
 }
-abstract class _B&Object&A = core::Object with self::A {
+abstract class _B&Object&A = core::Object with self::A /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.expect
index 238f1add3c9..3b19a6c2e26 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.expect
@@ -17,7 +17,7 @@ class A extends core::Object implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::A::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _B&Object&A = core::Object with self::A {
+abstract class _B&Object&A = core::Object with self::A /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.transformed.expect
index c9858761fe3..44e754ac340 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/forwarders_not_assumed_from_mixin.dart.strong.transformed.expect
@@ -17,7 +17,7 @@ class A extends core::Object implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::A::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _B&Object&A extends core::Object implements self::A {
+abstract class _B&Object&A extends core::Object implements self::A /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.outline.expect
index f968d951010..7dd0cad6f06 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.outline.expect
@@ -16,7 +16,7 @@ class M extends core::Object {
   method noSuchMethod(core::Invocation* i) → dynamic
     ;
 }
-abstract class _A&Object&M = core::Object with self::M {
+abstract class _A&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
@@ -27,7 +27,7 @@ class A extends self::_A&Object&M implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::M::noSuchMethod}(new core::_InvocationMirror::_withType(#foo, 0, const <core::Type*>[], const <dynamic>[], core::Map::unmodifiable<core::Symbol*, dynamic>(const <core::Symbol*, dynamic>{})));
 }
-abstract class _B&Object&M = core::Object with self::M {
+abstract class _B&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.expect
index 489451d21ad..46f85315e8c 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.expect
@@ -18,7 +18,7 @@ class M extends core::Object {
   method noSuchMethod(core::Invocation* i) → dynamic
     return null;
 }
-abstract class _A&Object&M = core::Object with self::M {
+abstract class _A&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
@@ -30,7 +30,7 @@ class A extends self::_A&Object&M implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::M::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _B&Object&M = core::Object with self::M {
+abstract class _B&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.transformed.expect
index 3d08a751dfd..32bc4ba1d54 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/interface_with_nsm.dart.strong.transformed.expect
@@ -18,7 +18,7 @@ class M extends core::Object {
   method noSuchMethod(core::Invocation* i) → dynamic
     return null;
 }
-abstract class _A&Object&M extends core::Object implements self::M {
+abstract class _A&Object&M extends core::Object implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
@@ -32,7 +32,7 @@ class A extends self::_A&Object&M implements self::I {
   no-such-method-forwarder method foo() → void
     return this.{self::M::noSuchMethod}(new core::_InvocationMirror::_withType(#C1, 0, #C2, #C3, core::Map::unmodifiable<core::Symbol*, dynamic>(#C4)));
 }
-abstract class _B&Object&M extends core::Object implements self::M {
+abstract class _B&Object&M extends core::Object implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.outline.expect
index de8e57b11d3..cd0cff0f143 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.outline.expect
@@ -8,7 +8,7 @@ class A extends core::Object {
   method noSuchMethod(core::Invocation* i) → dynamic
     ;
 }
-abstract class _B&Object&A = core::Object with self::A {
+abstract class _B&Object&A = core::Object with self::A /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.expect
index b7294d2a9a4..8b0741b824d 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.expect
@@ -10,7 +10,7 @@ class A extends core::Object {
     return null;
   }
 }
-abstract class _B&Object&A = core::Object with self::A {
+abstract class _B&Object&A = core::Object with self::A /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.transformed.expect
index 5da9029bcef..25949752715 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/nsm_mixed_in.dart.strong.transformed.expect
@@ -10,7 +10,7 @@ class A extends core::Object {
     return null;
   }
 }
-abstract class _B&Object&A extends core::Object implements self::A {
+abstract class _B&Object&A extends core::Object implements self::A /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_B&Object&A*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.outline.expect b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.outline.expect
index 6983d4754a5..96ee1929627 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.outline.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.outline.expect
@@ -13,7 +13,7 @@ class M extends core::Object {
   method noSuchMethod(core::Invocation* i) → dynamic
     ;
 }
-abstract class _A&Object&M = core::Object with self::M {
+abstract class _A&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.expect b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.expect
index 64693b85fc4..9cef3bac967 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.expect
@@ -16,7 +16,7 @@ class M extends core::Object {
     return null;
   }
 }
-abstract class _A&Object&M = core::Object with self::M {
+abstract class _A&Object&M = core::Object with self::M /*isAnonymousMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.transformed.expect b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.transformed.expect
index fe3fabb24b1..53a29592f7e 100644
--- a/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/no_such_method_forwarders/subst_on_forwarder.dart.strong.transformed.expect
@@ -16,7 +16,7 @@ class M extends core::Object {
     return null;
   }
 }
-abstract class _A&Object&M extends core::Object implements self::M {
+abstract class _A&Object&M extends core::Object implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   const synthetic constructor •() → self::_A&Object&M*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.outline.expect b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.outline.expect
index dfa4ba420bb..5e82d74c36e 100644
--- a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.outline.expect
@@ -10,7 +10,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_constructor_redirection.dart:6:21: Error: Too many positional arguments: 0 allowed, but 1 found.
 Try removing the extra positional arguments.
diff --git a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.expect b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.expect
index af2f9ebee4e..f345e51dbd0 100644
--- a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.expect
@@ -10,7 +10,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_constructor_redirection.dart:6:21: Error: Too many positional arguments: 0 allowed, but 1 found.
 Try removing the extra positional arguments.
diff --git a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.transformed.expect
index af2f9ebee4e..f345e51dbd0 100644
--- a/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/bad_constructor_redirection.dart.strong.transformed.expect
@@ -10,7 +10,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_constructor_redirection.dart:6:21: Error: Too many positional arguments: 0 allowed, but 1 found.
 Try removing the extra positional arguments.
diff --git a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.outline.expect b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.outline.expect
index a7b109916f3..55cdfbb3ebf 100644
--- a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.outline.expect
@@ -13,7 +13,7 @@ class A extends core::Object {
   constructor •(dynamic x) → self::A*
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart:10:20: Error: Too few positional arguments: 1 required, 0 given.
   const B() : super();
diff --git a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.expect b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.expect
index 1feb3f4b887..8fdc2b1ddd7 100644
--- a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.expect
@@ -14,7 +14,7 @@ class A extends core::Object {
     : super core::Object::•()
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart:10:20: Error: Too few positional arguments: 1 required, 0 given.
   const B() : super();
diff --git a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.transformed.expect
index 1feb3f4b887..8fdc2b1ddd7 100644
--- a/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart.strong.transformed.expect
@@ -14,7 +14,7 @@ class A extends core::Object {
     : super core::Object::•()
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_explicit_super_constructor.dart:10:20: Error: Too few positional arguments: 1 required, 0 given.
   const B() : super();
diff --git a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.outline.expect b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.outline.expect
index 57359a4c20d..8988c624111 100644
--- a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.outline.expect
@@ -13,7 +13,7 @@ class A extends core::Object {
   constructor •(dynamic x) → self::A*
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart:10:9: Error: The superclass, 'A', has no unnamed constructor that takes no arguments.
   const B();
diff --git a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.expect b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.expect
index 0ddc60f383e..3274e8eb766 100644
--- a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.expect
@@ -20,7 +20,7 @@ class A extends core::Object {
          ^"
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart:10:9: Error: The superclass, 'A', has no unnamed constructor that takes no arguments.
   const B();
diff --git a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.transformed.expect
index 0ddc60f383e..3274e8eb766 100644
--- a/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class A extends core::Object {
          ^"
     ;
 }
-class B extends self::A {
+class B extends self::A /*hasConstConstructor*/  {
   const constructor •() → self::B*
     : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/bad_implicit_super_constructor.dart:10:9: Error: The superclass, 'A', has no unnamed constructor that takes no arguments.
   const B();
diff --git a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.outline.expect b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.outline.expect
index 0451f5c7ad8..06242905cd8 100644
--- a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.outline.expect
@@ -7,12 +7,12 @@ class Mixin extends core::Object {
   synthetic constructor •() → self::Mixin*
     ;
 }
-abstract class _A&Object&Mixin = core::Object with self::Mixin {
+abstract class _A&Object&Mixin = core::Object with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&Object&Mixin*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&Mixin&Mixin = self::_A&Object&Mixin with self::Mixin {
+abstract class _A&Object&Mixin&Mixin = self::_A&Object&Mixin with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&Object&Mixin&Mixin*
     : super self::_A&Object&Mixin::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.expect b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.expect
index 6b3d4645a98..c8be9f90b9e 100644
--- a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.expect
@@ -8,12 +8,12 @@ class Mixin extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&Mixin = core::Object with self::Mixin {
+abstract class _A&Object&Mixin = core::Object with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&Object&Mixin*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&Mixin&Mixin = self::_A&Object&Mixin with self::Mixin {
+abstract class _A&Object&Mixin&Mixin = self::_A&Object&Mixin with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_A&Object&Mixin&Mixin*
     : super self::_A&Object&Mixin::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.transformed.expect
index ea7db2bfe5e..3d74ab66abd 100644
--- a/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/duplicated_mixin.dart.strong.transformed.expect
@@ -8,13 +8,13 @@ class Mixin extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&Mixin extends core::Object implements self::Mixin {
+abstract class _A&Object&Mixin extends core::Object implements self::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic field = null;
   synthetic constructor •() → self::_A&Object&Mixin*
     : super core::Object::•()
     ;
 }
-abstract class _A&Object&Mixin&Mixin extends self::_A&Object&Mixin implements self::Mixin {
+abstract class _A&Object&Mixin&Mixin extends self::_A&Object&Mixin implements self::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic field = null;
   synthetic constructor •() → self::_A&Object&Mixin&Mixin*
     : super self::_A&Object&Mixin::•()
diff --git a/pkg/front_end/testcases/rasta/enum.dart.outline.expect b/pkg/front_end/testcases/rasta/enum.dart.outline.expect
index 984ceebe6f4..bd3b3c5ce3d 100644
--- a/pkg/front_end/testcases/rasta/enum.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/enum.dart.outline.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = const <self::Foo*>[self::Foo::ec1, self::Foo::ec2];
diff --git a/pkg/front_end/testcases/rasta/enum.dart.strong.expect b/pkg/front_end/testcases/rasta/enum.dart.strong.expect
index ced26a8c120..690a0acc577 100644
--- a/pkg/front_end/testcases/rasta/enum.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/enum.dart.strong.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C7;
diff --git a/pkg/front_end/testcases/rasta/enum.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/enum.dart.strong.transformed.expect
index ced26a8c120..690a0acc577 100644
--- a/pkg/front_end/testcases/rasta/enum.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/enum.dart.strong.transformed.expect
@@ -2,7 +2,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class Foo extends core::Object {
+class Foo extends core::Object /*isEnum*/  {
   final field core::int* index;
   final field core::String* _name;
   static const field core::List<self::Foo*>* values = #C7;
diff --git a/pkg/front_end/testcases/rasta/issue_000007.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000007.dart.outline.expect
index 8d54f1edc2e..03798909999 100644
--- a/pkg/front_end/testcases/rasta/issue_000007.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000007.dart.outline.expect
@@ -12,7 +12,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     ;
 }
-abstract class _Sub&Base&Mixin = self::Base with self::Mixin {
+abstract class _Sub&Base&Mixin = self::Base with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Sub&Base&Mixin*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000007.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000007.dart.strong.expect
index 8aea3e874a2..655d4a798ea 100644
--- a/pkg/front_end/testcases/rasta/issue_000007.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000007.dart.strong.expect
@@ -14,7 +14,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     return core::print("foo");
 }
-abstract class _Sub&Base&Mixin = self::Base with self::Mixin {
+abstract class _Sub&Base&Mixin = self::Base with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Sub&Base&Mixin*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000007.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000007.dart.strong.transformed.expect
index 0c4886a88ca..9c25751e6a9 100644
--- a/pkg/front_end/testcases/rasta/issue_000007.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000007.dart.strong.transformed.expect
@@ -14,7 +14,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     return core::print("foo");
 }
-abstract class _Sub&Base&Mixin extends self::Base implements self::Mixin {
+abstract class _Sub&Base&Mixin extends self::Base implements self::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_Sub&Base&Mixin*
     : super self::Base::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000034.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000034.dart.outline.expect
index 02e6d34a405..3bfabf70f11 100644
--- a/pkg/front_end/testcases/rasta/issue_000034.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000034.dart.outline.expect
@@ -14,7 +14,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/issue_000034.dart:6:15: Error: This couldn't be parsed.
   const C() : this.x;
diff --git a/pkg/front_end/testcases/rasta/issue_000034.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000034.dart.strong.expect
index e901592e8f3..0f316bba213 100644
--- a/pkg/front_end/testcases/rasta/issue_000034.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000034.dart.strong.expect
@@ -14,7 +14,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/issue_000034.dart:6:15: Error: This couldn't be parsed.
   const C() : this.x;
diff --git a/pkg/front_end/testcases/rasta/issue_000034.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000034.dart.strong.transformed.expect
index e901592e8f3..0f316bba213 100644
--- a/pkg/front_end/testcases/rasta/issue_000034.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000034.dart.strong.transformed.expect
@@ -14,7 +14,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   const constructor •() → self::C*
     : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/issue_000034.dart:6:15: Error: This couldn't be parsed.
   const C() : this.x;
diff --git a/pkg/front_end/testcases/rasta/issue_000044.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000044.dart.outline.expect
index cd96d0fdb44..c4ff1331847 100644
--- a/pkg/front_end/testcases/rasta/issue_000044.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000044.dart.outline.expect
@@ -28,7 +28,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::C::good];
   const constructor constant() → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/rasta/issue_000044.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000044.dart.strong.expect
index 9c3fa75630f..1673fff187f 100644
--- a/pkg/front_end/testcases/rasta/issue_000044.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000044.dart.strong.expect
@@ -62,7 +62,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::C::good];
   const constructor constant() → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/rasta/issue_000044.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000044.dart.strong.transformed.expect
index e5760618179..211952aa6ad 100644
--- a/pkg/front_end/testcases/rasta/issue_000044.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000044.dart.strong.transformed.expect
@@ -62,7 +62,7 @@ library;
 import self as self;
 import "dart:core" as core;
 
-class C extends core::Object {
+class C extends core::Object /*hasConstConstructor*/  {
   static field dynamic _redirecting# = <dynamic>[self::C::good];
   const constructor constant() → self::C*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/rasta/issue_000048.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000048.dart.strong.transformed.expect
index ed8c0720bd0..47945f6f515 100644
--- a/pkg/front_end/testcases/rasta/issue_000048.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000048.dart.strong.transformed.expect
@@ -15,7 +15,7 @@ class M1 extends core::Object {
     : super core::Object::•()
     ;
 }
-class C extends self::A implements self::M1 {
+class C extends self::A implements self::M1 /*isEliminatedMixin*/  {
   field core::num* v2 = 0;
   synthetic constructor •(core::bool* v1, core::num* v2) → self::C*
     : super self::A::•(v1, v2)
diff --git a/pkg/front_end/testcases/rasta/issue_000070.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000070.dart.outline.expect
index c7a0e8162cf..26f75a55820 100644
--- a/pkg/front_end/testcases/rasta/issue_000070.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000070.dart.outline.expect
@@ -4,7 +4,7 @@ import "dart:core" as core;
 
 import "package:expect/expect.dart";
 
-class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object {
+class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field core::List<self::A::U*>* field;
   constructor •(self::A::N* n, self::A::S* s) → self::A<self::A::N*, self::A::S*, self::A::U*>*
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000070.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000070.dart.strong.expect
index 871861048ca..08f02742cff 100644
--- a/pkg/front_end/testcases/rasta/issue_000070.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000070.dart.strong.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object {
+class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field core::List<self::A::U*>* field;
   constructor •(self::A::N* n, self::A::S* s) → self::A<self::A::N*, self::A::S*, self::A::U*>*
     : self::A::field = core::List::•<self::A::U*>(), super core::Object::•() {
diff --git a/pkg/front_end/testcases/rasta/issue_000070.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000070.dart.strong.transformed.expect
index e5097ea2364..44a777c0e43 100644
--- a/pkg/front_end/testcases/rasta/issue_000070.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000070.dart.strong.transformed.expect
@@ -5,7 +5,7 @@ import "package:expect/expect.dart" as exp;
 
 import "package:expect/expect.dart";
 
-class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object {
+class A<N extends core::Object* = dynamic, S extends core::Object* = dynamic, U extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   final field core::List<self::A::U*>* field;
   constructor •(self::A::N* n, self::A::S* s) → self::A<self::A::N*, self::A::S*, self::A::U*>*
     : self::A::field = core::_GrowableList::•<self::A::U*>(0), super core::Object::•() {
diff --git a/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
index ef157190021..99bda27c0be 100644
--- a/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
@@ -9,7 +9,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     ;
 }
-abstract class _Foo&Object&Mixin = core::Object with self::Mixin {
+abstract class _Foo&Object&Mixin = core::Object with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&Mixin*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000080.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000080.dart.strong.expect
index c7b2aaa9acf..6a193ab75cb 100644
--- a/pkg/front_end/testcases/rasta/issue_000080.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000080.dart.strong.expect
@@ -10,7 +10,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     return 87;
 }
-abstract class _Foo&Object&Mixin = core::Object with self::Mixin {
+abstract class _Foo&Object&Mixin = core::Object with self::Mixin /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_Foo&Object&Mixin*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/issue_000080.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000080.dart.strong.transformed.expect
index 37e2112b572..5f31625a5e1 100644
--- a/pkg/front_end/testcases/rasta/issue_000080.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000080.dart.strong.transformed.expect
@@ -10,7 +10,7 @@ class Mixin extends core::Object {
   method foo() → dynamic
     return 87;
 }
-abstract class _Foo&Object&Mixin extends core::Object implements self::Mixin {
+abstract class _Foo&Object&Mixin extends core::Object implements self::Mixin /*isAnonymousMixin,isEliminatedMixin*/  {
   field dynamic field = null;
   synthetic constructor •() → self::_Foo&Object&Mixin*
     : super core::Object::•()
diff --git a/pkg/front_end/testcases/rasta/super_mixin.dart.outline.expect b/pkg/front_end/testcases/rasta/super_mixin.dart.outline.expect
index 4d67319b8e2..1966a898ae1 100644
--- a/pkg/front_end/testcases/rasta/super_mixin.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/super_mixin.dart.outline.expect
@@ -13,7 +13,7 @@ class Super<S extends core::Object* = dynamic> extends core::Object {
   method f() → dynamic
     ;
 }
-abstract class _C&Super&Mixin<V extends core::Object* = dynamic> = self::Super<self::_C&Super&Mixin::V*> with mix::Mixin<self::_C&Super&Mixin::V*> {
+abstract class _C&Super&Mixin<V extends core::Object* = dynamic> = self::Super<self::_C&Super&Mixin::V*> with mix::Mixin<self::_C&Super&Mixin::V*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&Super&Mixin<self::_C&Super&Mixin::V*>*
     : super self::Super::•()
     ;
@@ -22,7 +22,7 @@ class C<V extends core::Object* = dynamic> extends self::_C&Super&Mixin<self::C:
   synthetic constructor •() → self::C<self::C::V*>*
     ;
 }
-abstract class _D&Super&Mixin = self::Super<dynamic> with mix::Mixin<dynamic> {
+abstract class _D&Super&Mixin = self::Super<dynamic> with mix::Mixin<dynamic> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&Super&Mixin*
     : super self::Super::•()
     ;
diff --git a/pkg/front_end/testcases/rasta/super_mixin.dart.strong.expect b/pkg/front_end/testcases/rasta/super_mixin.dart.strong.expect
index 70eed776c05..30d7ed65ffe 100644
--- a/pkg/front_end/testcases/rasta/super_mixin.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/super_mixin.dart.strong.expect
@@ -14,7 +14,7 @@ class Super<S extends core::Object* = dynamic> extends core::Object {
   method f() → dynamic
     return 3;
 }
-abstract class _C&Super&Mixin<V extends core::Object* = dynamic> = self::Super<self::_C&Super&Mixin::V*> with mix::Mixin<self::_C&Super&Mixin::V*> {
+abstract class _C&Super&Mixin<V extends core::Object* = dynamic> = self::Super<self::_C&Super&Mixin::V*> with mix::Mixin<self::_C&Super&Mixin::V*> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&Super&Mixin<self::_C&Super&Mixin::V*>*
     : super self::Super::•()
     ;
@@ -24,7 +24,7 @@ class C<V extends core::Object* = dynamic> extends self::_C&Super&Mixin<self::C:
     : super self::_C&Super&Mixin::•()
     ;
 }
-abstract class _D&Super&Mixin = self::Super<dynamic> with mix::Mixin<dynamic> {
+abstract class _D&Super&Mixin = self::Super<dynamic> with mix::Mixin<dynamic> /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_D&Super&Mixin*
     : super self::Super::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_32182.dart.outline.expect b/pkg/front_end/testcases/regress/issue_32182.dart.outline.expect
index 426b983e545..dbbd56353f1 100644
--- a/pkg/front_end/testcases/regress/issue_32182.dart.outline.expect
+++ b/pkg/front_end/testcases/regress/issue_32182.dart.outline.expect
@@ -14,7 +14,7 @@ class M extends core::Object {
   method m() → dynamic
     ;
 }
-abstract class _C&A&M = self::A<self::A<dynamic>*> with self::M {
+abstract class _C&A&M = self::A<self::A<dynamic>*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&A&M*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_32182.dart.strong.expect b/pkg/front_end/testcases/regress/issue_32182.dart.strong.expect
index e8d1b928721..12c9067bc27 100644
--- a/pkg/front_end/testcases/regress/issue_32182.dart.strong.expect
+++ b/pkg/front_end/testcases/regress/issue_32182.dart.strong.expect
@@ -16,7 +16,7 @@ class M extends core::Object {
   method m() → dynamic
     return 42;
 }
-abstract class _C&A&M = self::A<self::A<dynamic>*> with self::M {
+abstract class _C&A&M = self::A<self::A<dynamic>*> with self::M /*isAnonymousMixin*/  {
   synthetic constructor •() → self::_C&A&M*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_32182.dart.strong.transformed.expect b/pkg/front_end/testcases/regress/issue_32182.dart.strong.transformed.expect
index 23695783cc9..90d83a5b33f 100644
--- a/pkg/front_end/testcases/regress/issue_32182.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/regress/issue_32182.dart.strong.transformed.expect
@@ -16,7 +16,7 @@ class M extends core::Object {
   method m() → dynamic
     return 42;
 }
-abstract class _C&A&M extends self::A<self::A<dynamic>*> implements self::M {
+abstract class _C&A&M extends self::A<self::A<dynamic>*> implements self::M /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_C&A&M*
     : super self::A::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_34403.dart.outline.expect b/pkg/front_end/testcases/regress/issue_34403.dart.outline.expect
index 0983f9985c1..ea7359e99fc 100644
--- a/pkg/front_end/testcases/regress/issue_34403.dart.outline.expect
+++ b/pkg/front_end/testcases/regress/issue_34403.dart.outline.expect
@@ -8,7 +8,7 @@ class C<T extends core::Object* = dynamic> extends core::Object {
   constructor bar() → self::C<self::C::T*>*
     ;
 }
-class D<T extends core::Object* = dynamic> extends core::Object {
+class D<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
@@ -24,7 +24,7 @@ class E<T extends core::Object* = dynamic> extends core::Object {
   constructor bar() → self2::E<self2::E::T*>*
     ;
 }
-class F<T extends core::Object* = dynamic> extends core::Object {
+class F<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self2::F<self2::F::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_34403.dart.strong.expect b/pkg/front_end/testcases/regress/issue_34403.dart.strong.expect
index cd83b085445..f6fd766cec6 100644
--- a/pkg/front_end/testcases/regress/issue_34403.dart.strong.expect
+++ b/pkg/front_end/testcases/regress/issue_34403.dart.strong.expect
@@ -93,7 +93,7 @@ class C<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class D<T extends core::Object* = dynamic> extends core::Object {
+class D<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
@@ -134,7 +134,7 @@ class E<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class F<T extends core::Object* = dynamic> extends core::Object {
+class F<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → iss::F<iss::F::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_34403.dart.strong.transformed.expect b/pkg/front_end/testcases/regress/issue_34403.dart.strong.transformed.expect
index cd83b085445..f6fd766cec6 100644
--- a/pkg/front_end/testcases/regress/issue_34403.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/regress/issue_34403.dart.strong.transformed.expect
@@ -93,7 +93,7 @@ class C<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class D<T extends core::Object* = dynamic> extends core::Object {
+class D<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → self::D<self::D::T*>*
     : super core::Object::•()
     ;
@@ -134,7 +134,7 @@ class E<T extends core::Object* = dynamic> extends core::Object {
     : super core::Object::•()
     ;
 }
-class F<T extends core::Object* = dynamic> extends core::Object {
+class F<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
   const constructor foo() → iss::F<iss::F::T*>*
     : super core::Object::•()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_34563.dart.outline.expect b/pkg/front_end/testcases/regress/issue_34563.dart.outline.expect
index 1988ac5a697..db5ac39ccd8 100644
--- a/pkg/front_end/testcases/regress/issue_34563.dart.outline.expect
+++ b/pkg/front_end/testcases/regress/issue_34563.dart.outline.expect
@@ -21,13 +21,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class M1 extends core::Object {
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
   get m() → core::int*
     ;
 }
-abstract class M2 extends core::Object {
+abstract class M2 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class M3 extends core::Object {
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
 }
 class C1 extends core::Object {
   synthetic constructor •() → self::C1*
diff --git a/pkg/front_end/testcases/regress/issue_34563.dart.strong.expect b/pkg/front_end/testcases/regress/issue_34563.dart.strong.expect
index 4410636c8a5..e254b75a7ff 100644
--- a/pkg/front_end/testcases/regress/issue_34563.dart.strong.expect
+++ b/pkg/front_end/testcases/regress/issue_34563.dart.strong.expect
@@ -45,13 +45,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class M1 extends core::Object {
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
   get m() → core::int*
     return 1;
 }
-abstract class M2 extends core::Object {
+abstract class M2 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class M3 extends core::Object {
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
 }
 class C1 extends core::Object {
   synthetic constructor •() → self::C1*
diff --git a/pkg/front_end/testcases/regress/issue_34563.dart.strong.transformed.expect b/pkg/front_end/testcases/regress/issue_34563.dart.strong.transformed.expect
index 4410636c8a5..e254b75a7ff 100644
--- a/pkg/front_end/testcases/regress/issue_34563.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/regress/issue_34563.dart.strong.transformed.expect
@@ -45,13 +45,13 @@ library;
 import self as self;
 import "dart:core" as core;
 
-abstract class M1 extends core::Object {
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
   get m() → core::int*
     return 1;
 }
-abstract class M2 extends core::Object {
+abstract class M2 extends core::Object /*isMixinDeclaration*/  {
 }
-abstract class M3 extends core::Object {
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
 }
 class C1 extends core::Object {
   synthetic constructor •() → self::C1*
diff --git a/pkg/front_end/testcases/regress/issue_36669.dart.outline.expect b/pkg/front_end/testcases/regress/issue_36669.dart.outline.expect
index 9684d36713e..1e624679125 100644
--- a/pkg/front_end/testcases/regress/issue_36669.dart.outline.expect
+++ b/pkg/front_end/testcases/regress/issue_36669.dart.outline.expect
@@ -10,7 +10,7 @@ class MixMeIn extends core::Object {
   synthetic constructor •() → self::MixMeIn*
     ;
 }
-abstract class _Foo&NoUnnamedConstuctor&MixMeIn = self::NoUnnamedConstuctor with self::MixMeIn {
+abstract class _Foo&NoUnnamedConstuctor&MixMeIn = self::NoUnnamedConstuctor with self::MixMeIn /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_Foo&NoUnnamedConstuctor&MixMeIn*
     : super self::NoUnnamedConstuctor::_()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_36669.dart.strong.expect b/pkg/front_end/testcases/regress/issue_36669.dart.strong.expect
index 175b974d66e..5ea619eb7a7 100644
--- a/pkg/front_end/testcases/regress/issue_36669.dart.strong.expect
+++ b/pkg/front_end/testcases/regress/issue_36669.dart.strong.expect
@@ -19,7 +19,7 @@ class MixMeIn extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&NoUnnamedConstuctor&MixMeIn = self::NoUnnamedConstuctor with self::MixMeIn {
+abstract class _Foo&NoUnnamedConstuctor&MixMeIn = self::NoUnnamedConstuctor with self::MixMeIn /*isAnonymousMixin*/  {
   synthetic constructor _() → self::_Foo&NoUnnamedConstuctor&MixMeIn*
     : super self::NoUnnamedConstuctor::_()
     ;
diff --git a/pkg/front_end/testcases/regress/issue_36669.dart.strong.transformed.expect b/pkg/front_end/testcases/regress/issue_36669.dart.strong.transformed.expect
index f15581b5d3c..837887c38b4 100644
--- a/pkg/front_end/testcases/regress/issue_36669.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/regress/issue_36669.dart.strong.transformed.expect
@@ -19,7 +19,7 @@ class MixMeIn extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _Foo&NoUnnamedConstuctor&MixMeIn extends self::NoUnnamedConstuctor implements self::MixMeIn {
+abstract class _Foo&NoUnnamedConstuctor&MixMeIn extends self::NoUnnamedConstuctor implements self::MixMeIn /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor _() → self::_Foo&NoUnnamedConstuctor&MixMeIn*
     : super self::NoUnnamedConstuctor::_()
     ;
diff --git a/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_mixin.dart.strong.transformed.expect
index e63cbdbc843..bf75e8d7fdc 100644
--- a/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_mixin.dart.strong.transformed.expect
@@ -20,7 +20,7 @@ class M extends core::Object {
     ;
   method f(core::int* x) → void {}
 }
-class C extends self::B implements self::I<core::int*>, self::M {
+class C extends self::B implements self::I<core::int*>, self::M /*isEliminatedMixin*/  {
   synthetic constructor •() → self::C*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_super_mixin.dart.strong.transformed.expect b/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_super_mixin.dart.strong.transformed.expect
index fc8cb4a1df4..99f6d1fc889 100644
--- a/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_super_mixin.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/runtime_checks/covariant_generic_parameter_in_interface_super_mixin.dart.strong.transformed.expect
@@ -19,7 +19,7 @@ class M extends core::Object {
     : super core::Object::•()
     ;
 }
-class C extends self::B implements self::I<core::int*>, self::M {
+class C extends self::B implements self::I<core::int*>, self::M /*isEliminatedMixin*/  {
   synthetic constructor •() → self::C*
     : super self::B::•()
     ;
diff --git a/pkg/front_end/testcases/text_serialization.status b/pkg/front_end/testcases/text_serialization.status
index 45b9a171607..b681515cdaa 100644
--- a/pkg/front_end/testcases/text_serialization.status
+++ b/pkg/front_end/testcases/text_serialization.status
@@ -1241,6 +1241,8 @@ nnbd/member_inheritance_from_opt_out: TextSerializationFailure
 nnbd/messages_with_types_opt_in: TypeCheckError
 nnbd/messages_with_types_opt_out: TypeCheckError
 nnbd/missing_required_named_parameter: TextSerializationFailure
+nnbd/mixin_from_opt_in: TextSerializationFailure
+nnbd/mixin_from_opt_out: TextSerializationFailure
 nnbd/never_receiver: TextSerializationFailure
 nnbd/nnbd_opt_out_language_version: TextSerializationFailure
 nnbd/nnbd_opt_out_language_version_try_to_trick: TextSerializationFailure
diff --git a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.outline.expect b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.outline.expect
index 44fe61abe9f..aca96a6e232 100644
--- a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.outline.expect
+++ b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.outline.expect
@@ -6,7 +6,7 @@ class A extends core::Object {
   synthetic constructor •() → self::A*
     ;
 }
-abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A {
+abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A /*isMixinDeclaration*/  {
 }
 static method main() → dynamic
   ;
diff --git a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.expect b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.expect
index 0c6c3cdf00a..f0cf002a4dd 100644
--- a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.expect
+++ b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.expect
@@ -7,6 +7,6 @@ class A extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A {
+abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A /*isMixinDeclaration*/  {
 }
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.transformed.expect b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.transformed.expect
index 0c6c3cdf00a..f0cf002a4dd 100644
--- a/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/variance/mixin_type_parameter_modifier.dart.strong.transformed.expect
@@ -7,6 +7,6 @@ class A extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A {
+abstract class B<invariant X extends core::Object* = dynamic, Y extends core::Object* = dynamic, contravariant Z extends core::Object* = dynamic> extends self::A /*isMixinDeclaration*/  {
 }
 static method main() → dynamic {}
diff --git a/pkg/kernel/binary.md b/pkg/kernel/binary.md
index 6c70435083a..2762192b67f 100644
--- a/pkg/kernel/binary.md
+++ b/pkg/kernel/binary.md
@@ -143,7 +143,7 @@ type CanonicalName {
 
 type ComponentFile {
   UInt32 magic = 0x90ABCDEF;
-  UInt32 formatVersion = 38;
+  UInt32 formatVersion = 39;
   List<String> problemsAsJson; // Described in problems.md.
   Library[] libraries;
   UriSource sourceMap;
@@ -317,7 +317,8 @@ type Class extends Node {
   FileOffset fileOffset; // Offset of the name of the class.
   FileOffset fileEndOffset;
   Byte flags (levelBit0, levelBit1, isAbstract, isEnum, isAnonymousMixin,
-              isEliminatedMixin, isMixinDeclaration); // Where level is index into ClassLevel
+              isEliminatedMixin, isMixinDeclaration, 
+              hasConstConstructor); // Where level is index into ClassLevel
   StringReference name;
   List<Expression> annotations;
   List<TypeParameter> typeParameters;
@@ -367,7 +368,8 @@ type Field extends Member {
   FileOffset fileOffset;
   FileOffset fileEndOffset;
   UInt flags (isFinal, isConst, isStatic, hasImplicitGetter, hasImplicitSetter,
-                isCovariant, isGenericCovariantImpl, isLate, isExtensionMember);
+                isCovariant, isGenericCovariantImpl, isLate, isExtensionMember,
+                isNonNullableByDefault);
   Name name;
   List<Expression> annotations;
   DartType type;
@@ -381,7 +383,7 @@ type Constructor extends Member {
   FileOffset startFileOffset; // Offset of the start of the constructor including any annotations.
   FileOffset fileOffset; // Offset of the constructor name.
   FileOffset fileEndOffset;
-  Byte flags (isConst, isExternal, isSynthetic);
+  Byte flags (isConst, isExternal, isSynthetic, isNonNullableByDefault);
   Name name;
   List<Expression> annotations;
   FunctionNode function;
@@ -409,7 +411,8 @@ type Procedure extends Member {
   Byte kind; // Index into the ProcedureKind enum above.
   UInt flags (isStatic, isAbstract, isExternal, isConst, isForwardingStub,
               isForwardingSemiStub, isRedirectingFactoryConstructor,
-              isNoSuchMethodForwarder, isExtensionMember, isMemberSignature);
+              isNoSuchMethodForwarder, isExtensionMember, isMemberSignature,
+              isNonNullableByDefault);
   Name name;
   List<Expression> annotations;
   // Only present if the 'isForwardingStub' flag is set.
diff --git a/pkg/kernel/lib/ast.dart b/pkg/kernel/lib/ast.dart
index 1b452d2c434..141595f9fbf 100644
--- a/pkg/kernel/lib/ast.dart
+++ b/pkg/kernel/lib/ast.dart
@@ -913,6 +913,7 @@ class Class extends NamedNode implements Annotatable, FileUriNode {
   static const int FlagAnonymousMixin = 1 << 4;
   static const int FlagEliminatedMixin = 1 << 5;
   static const int FlagMixinDeclaration = 1 << 6;
+  static const int FlagHasConstConstructor = 1 << 7;
 
   int flags = 0;
 
@@ -971,6 +972,15 @@ class Class extends NamedNode implements Annotatable, FileUriNode {
         : (flags & ~FlagMixinDeclaration);
   }
 
+  /// True if this class declares one or more constant constructors.
+  bool get hasConstConstructor => flags & FlagHasConstConstructor != 0;
+
+  void set hasConstConstructor(bool value) {
+    flags = value
+        ? (flags | FlagHasConstConstructor)
+        : (flags & ~FlagHasConstConstructor);
+  }
+
   List<Supertype> superclassConstraints() {
     var constraints = <Supertype>[];
 
@@ -1532,6 +1542,11 @@ abstract class Member extends NamedNode implements Annotatable, FileUriNode {
   ///
   bool get isExtensionMember;
 
+  /// If `true` this member is defined in a library for which non-nullable by
+  /// default is enabled.
+  bool get isNonNullableByDefault;
+  void set isNonNullableByDefault(bool value);
+
   /// The body of the procedure or constructor, or `null` if this is a field.
   FunctionNode get function => null;
 
@@ -1599,6 +1614,7 @@ class Field extends Member {
   static const int FlagGenericCovariantImpl = 1 << 6;
   static const int FlagLate = 1 << 7;
   static const int FlagExtensionMember = 1 << 8;
+  static const int FlagNonNullableByDefault = 1 << 9;
 
   /// Whether the field is declared with the `covariant` keyword.
   bool get isCovariant => flags & FlagCovariant != 0;
@@ -1694,6 +1710,16 @@ class Field extends Member {
     if (value) throw 'Fields cannot be external';
   }
 
+  @override
+  bool get isNonNullableByDefault => flags & FlagNonNullableByDefault != 0;
+
+  @override
+  void set isNonNullableByDefault(bool value) {
+    flags = value
+        ? (flags | FlagNonNullableByDefault)
+        : (flags & ~FlagNonNullableByDefault);
+  }
+
   R accept<R>(MemberVisitor<R> v) => v.visitField(this);
 
   acceptReference(MemberReferenceVisitor v) => v.visitFieldReference(this);
@@ -1766,6 +1792,7 @@ class Constructor extends Member {
   static const int FlagConst = 1 << 0; // Must match serialized bit positions.
   static const int FlagExternal = 1 << 1;
   static const int FlagSynthetic = 1 << 2;
+  static const int FlagNonNullableByDefault = 1 << 3;
 
   bool get isConst => flags & FlagConst != 0;
   bool get isExternal => flags & FlagExternal != 0;
@@ -1793,6 +1820,16 @@ class Constructor extends Member {
   @override
   bool get isExtensionMember => false;
 
+  @override
+  bool get isNonNullableByDefault => flags & FlagNonNullableByDefault != 0;
+
+  @override
+  void set isNonNullableByDefault(bool value) {
+    flags = value
+        ? (flags | FlagNonNullableByDefault)
+        : (flags & ~FlagNonNullableByDefault);
+  }
+
   R accept<R>(MemberVisitor<R> v) => v.visitConstructor(this);
 
   acceptReference(MemberReferenceVisitor v) =>
@@ -1901,6 +1938,7 @@ class RedirectingFactoryConstructor extends Member {
 
   static const int FlagConst = 1 << 0; // Must match serialized bit positions.
   static const int FlagExternal = 1 << 1;
+  static const int FlagNonNullableByDefault = 1 << 2;
 
   bool get isConst => flags & FlagConst != 0;
   bool get isExternal => flags & FlagExternal != 0;
@@ -1922,6 +1960,16 @@ class RedirectingFactoryConstructor extends Member {
 
   bool get isUnresolved => targetReference == null;
 
+  @override
+  bool get isNonNullableByDefault => flags & FlagNonNullableByDefault != 0;
+
+  @override
+  void set isNonNullableByDefault(bool value) {
+    flags = value
+        ? (flags | FlagNonNullableByDefault)
+        : (flags & ~FlagNonNullableByDefault);
+  }
+
   Member get target => targetReference?.asMember;
 
   void set target(Member member) {
@@ -2080,6 +2128,7 @@ class Procedure extends Member {
   static const int FlagNoSuchMethodForwarder = 1 << 7;
   static const int FlagExtensionMember = 1 << 8;
   static const int FlagMemberSignature = 1 << 9;
+  static const int FlagNonNullableByDefault = 1 << 10;
 
   bool get isStatic => flags & FlagStatic != 0;
   bool get isAbstract => flags & FlagAbstract != 0;
@@ -2185,6 +2234,16 @@ class Procedure extends Member {
   bool get hasSetter => kind == ProcedureKind.Setter;
   bool get isFactory => kind == ProcedureKind.Factory;
 
+  @override
+  bool get isNonNullableByDefault => flags & FlagNonNullableByDefault != 0;
+
+  @override
+  void set isNonNullableByDefault(bool value) {
+    flags = value
+        ? (flags | FlagNonNullableByDefault)
+        : (flags & ~FlagNonNullableByDefault);
+  }
+
   Member get forwardingStubSuperTarget =>
       forwardingStubSuperTargetReference?.asMember;
 
diff --git a/pkg/kernel/lib/binary/tag.dart b/pkg/kernel/lib/binary/tag.dart
index f45810bd9fa..dec7c711ce1 100644
--- a/pkg/kernel/lib/binary/tag.dart
+++ b/pkg/kernel/lib/binary/tag.dart
@@ -149,7 +149,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h, pkg/kernel/binary.md.
-  static const int BinaryFormatVersion = 38;
+  static const int BinaryFormatVersion = 39;
 }
 
 abstract class ConstantTag {
diff --git a/pkg/kernel/lib/text/ast_to_text.dart b/pkg/kernel/lib/text/ast_to_text.dart
index 06bd220e74c..0e32cb2f705 100644
--- a/pkg/kernel/lib/text/ast_to_text.dart
+++ b/pkg/kernel/lib/text/ast_to_text.dart
@@ -409,6 +409,9 @@ class Printer extends Visitor<Null> {
     if (library.name != null) {
       writeWord(library.name);
     }
+    if (library.isNonNullableByDefault) {
+      writeWord("/*isNonNullableByDefault*/");
+    }
     endLine(';');
 
     LibraryImportTable imports = new LibraryImportTable(library);
@@ -1071,11 +1074,23 @@ class Printer extends Visitor<Null> {
       writeSpaced('=');
       writeExpression(node.initializer);
     }
+    List<String> features = <String>[];
+    if (node.enclosingLibrary.isNonNullableByDefault !=
+        node.isNonNullableByDefault) {
+      if (node.isNonNullableByDefault) {
+        features.add("isNonNullableByDefault");
+      } else {
+        features.add("isNullableByDefault");
+      }
+    }
     if ((node.enclosingClass == null &&
             node.enclosingLibrary.fileUri != node.fileUri) ||
         (node.enclosingClass != null &&
             node.enclosingClass.fileUri != node.fileUri)) {
-      writeWord("/* from ${node.fileUri} */");
+      features.add(" from ${node.fileUri} ");
+    }
+    if (features.isNotEmpty) {
+      writeWord("/*${features.join(',')}*/");
     }
     endLine(';');
   }
@@ -1091,11 +1106,23 @@ class Printer extends Visitor<Null> {
     writeModifier(node.isMemberSignature, 'member-signature');
     writeModifier(node.isNoSuchMethodForwarder, 'no-such-method-forwarder');
     writeWord(procedureKindToString(node.kind));
+    List<String> features = <String>[];
+    if (node.enclosingLibrary.isNonNullableByDefault !=
+        node.isNonNullableByDefault) {
+      if (node.isNonNullableByDefault) {
+        features.add("isNonNullableByDefault");
+      } else {
+        features.add("isNullableByDefault");
+      }
+    }
     if ((node.enclosingClass == null &&
             node.enclosingLibrary.fileUri != node.fileUri) ||
         (node.enclosingClass != null &&
             node.enclosingClass.fileUri != node.fileUri)) {
-      writeWord("/* from ${node.fileUri} */");
+      features.add(" from ${node.fileUri} ");
+    }
+    if (features.isNotEmpty) {
+      writeWord("/*${features.join(',')}*/");
     }
     writeFunction(node.function, name: getMemberName(node));
   }
@@ -1107,6 +1134,18 @@ class Printer extends Visitor<Null> {
     writeModifier(node.isConst, 'const');
     writeModifier(node.isSynthetic, 'synthetic');
     writeWord('constructor');
+    List<String> features = <String>[];
+    if (node.enclosingLibrary.isNonNullableByDefault !=
+        node.isNonNullableByDefault) {
+      if (node.isNonNullableByDefault) {
+        features.add("isNonNullableByDefault");
+      } else {
+        features.add("isNullableByDefault");
+      }
+    }
+    if (features.isNotEmpty) {
+      writeWord("/*${features.join(',')}*/");
+    }
     writeFunction(node.function,
         name: node.name, initializers: node.initializers);
   }
@@ -1131,6 +1170,18 @@ class Printer extends Visitor<Null> {
       writeList(node.typeArguments, writeType);
       writeSymbol('>');
     }
+    List<String> features = <String>[];
+    if (node.enclosingLibrary.isNonNullableByDefault !=
+        node.isNonNullableByDefault) {
+      if (node.isNonNullableByDefault) {
+        features.add("isNonNullableByDefault");
+      } else {
+        features.add("isNullableByDefault");
+      }
+    }
+    if (features.isNotEmpty) {
+      writeWord("/*${features.join(',')}*/");
+    }
     endLine(';');
   }
 
@@ -1154,6 +1205,25 @@ class Printer extends Visitor<Null> {
       writeSpaced('implements');
       writeList(node.implementedTypes, visitSupertype);
     }
+    List<String> features = <String>[];
+    if (node.isEnum) {
+      features.add('isEnum');
+    }
+    if (node.isAnonymousMixin) {
+      features.add('isAnonymousMixin');
+    }
+    if (node.isEliminatedMixin) {
+      features.add('isEliminatedMixin');
+    }
+    if (node.isMixinDeclaration) {
+      features.add('isMixinDeclaration');
+    }
+    if (node.hasConstConstructor) {
+      features.add('hasConstConstructor');
+    }
+    if (features.isNotEmpty) {
+      writeSpaced('/*${features.join(',')}*/');
+    }
     var endLineString = ' {';
     if (node.enclosingLibrary.fileUri != node.fileUri) {
       endLineString += ' // from ${node.fileUri}';
diff --git a/pkg/vm/lib/transformations/ffi_definitions.dart b/pkg/vm/lib/transformations/ffi_definitions.dart
index 97aa0871f13..75ff955a998 100644
--- a/pkg/vm/lib/transformations/ffi_definitions.dart
+++ b/pkg/vm/lib/transformations/ffi_definitions.dart
@@ -244,7 +244,8 @@ class _FfiDefinitionTransformer extends FfiTransformer {
         ],
         fileUri: node.fileUri,
         reference: referenceFrom?.reference)
-      ..fileOffset = node.fileOffset;
+      ..fileOffset = node.fileOffset
+      ..isNonNullableByDefault = node.enclosingLibrary.isNonNullableByDefault;
     _makeEntryPoint(ctor);
     node.addMember(ctor);
   }
@@ -348,7 +349,8 @@ class _FfiDefinitionTransformer extends FfiTransformer {
         fileUri: field.fileUri,
         reference:
             indexedClass?.lookupProcedureNotSetter(pointerName.name)?.reference)
-      ..fileOffset = field.fileOffset;
+      ..fileOffset = field.fileOffset
+      ..isNonNullableByDefault = field.isNonNullableByDefault;
 
     // Sample output:
     // double get x => _xPtr.value;
@@ -369,7 +371,8 @@ class _FfiDefinitionTransformer extends FfiTransformer {
         fileUri: field.fileUri,
         reference:
             indexedClass?.lookupProcedureNotSetter(field.name.name)?.reference)
-      ..fileOffset = field.fileOffset;
+      ..fileOffset = field.fileOffset
+      ..isNonNullableByDefault = field.isNonNullableByDefault;
 
     // Sample output:
     // set x(double v) { _xPtr.value = v; };
@@ -395,7 +398,8 @@ class _FfiDefinitionTransformer extends FfiTransformer {
           fileUri: field.fileUri,
           reference:
               indexedClass?.lookupProcedureSetter(field.name.name)?.reference)
-        ..fileOffset = field.fileOffset;
+        ..fileOffset = field.fileOffset
+        ..isNonNullableByDefault = field.isNonNullableByDefault;
     }
 
     replacedGetters[field] = getter;
diff --git a/pkg/vm/testcases/bytecode/literals.dart.expect b/pkg/vm/testcases/bytecode/literals.dart.expect
index e90a55cd04d..316e2e46399 100644
--- a/pkg/vm/testcases/bytecode/literals.dart.expect
+++ b/pkg/vm/testcases/bytecode/literals.dart.expect
@@ -684,7 +684,7 @@ ConstantPool {
 ]library #lib from "#lib" as #lib {
 
   typedef GenericFunctionType = <X extends dart.core::Object* = dynamic>(X*) →* X*;
-  class A extends dart.core::Object {
+  class A extends dart.core::Object /*isEnum*/  {
     final field dart.core::int* index;
     final field dart.core::String* _name;
     static const field dart.core::List<#lib::A*>* values = #C13;
@@ -698,31 +698,31 @@ ConstantPool {
     method toString() → dart.core::String*
       return this.{=#lib::A::_name};
   }
-  class B extends dart.core::Object {
+  class B extends dart.core::Object /*hasConstConstructor*/  {
     final field dart.core::int* i;
     const constructor •(dart.core::int* i) → #lib::B*
       : #lib::B::i = i, super dart.core::Object::•()
       ;
   }
-  class C extends #lib::B {
+  class C extends #lib::B /*hasConstConstructor*/  {
     final field dart.core::int* j;
     const constructor •(dart.core::int* a, dart.core::int* b, dart.core::int* c) → #lib::C*
       : #lib::C::j = a.{dart.core::num::+}(b), super #lib::B::•(c.{dart.core::num::*}(5))
       ;
   }
-  class D extends dart.core::Object {
+  class D extends dart.core::Object /*hasConstConstructor*/  {
     final field dynamic x;
     final field dynamic y;
     const constructor •(dynamic x, [dynamic y = #C14]) → #lib::D*
       : #lib::D::x = x, #lib::D::y = y, super dart.core::Object::•()
       ;
   }
-  class E<T extends dart.core::Object* = dynamic> extends dart.core::Object {
+  class E<T extends dart.core::Object* = dynamic> extends dart.core::Object /*hasConstConstructor*/  {
     const constructor •() → #lib::E<#lib::E::T*>*
       : super dart.core::Object::•()
       ;
   }
-  class F<P extends dart.core::Object* = dynamic, Q extends dart.core::Object* = dynamic> extends #lib::E<dart.core::Map<#lib::F::P*, #lib::F::Q*>*> {
+  class F<P extends dart.core::Object* = dynamic, Q extends dart.core::Object* = dynamic> extends #lib::E<dart.core::Map<#lib::F::P*, #lib::F::Q*>*> /*hasConstConstructor*/  {
     const constructor •() → #lib::F<#lib::F::P*, #lib::F::Q*>*
       : super #lib::E::•()
       ;
diff --git a/pkg/vm/testcases/transformations/type_flow/transformer/annotation.dart.expect b/pkg/vm/testcases/transformations/type_flow/transformer/annotation.dart.expect
index ec084d3eb6d..a86626502fb 100644
--- a/pkg/vm/testcases/transformations/type_flow/transformer/annotation.dart.expect
+++ b/pkg/vm/testcases/transformations/type_flow/transformer/annotation.dart.expect
@@ -4,17 +4,17 @@ import "dart:core" as core;
 
 @#C5
 typedef SomeType<contravariant T extends core::Object* = dynamic> = (core::List<T*>*) →* void;
-abstract class ClassAnnotation2 extends core::Object {
+abstract class ClassAnnotation2 extends core::Object /*hasConstConstructor*/  {
 }
-abstract class MethodAnnotation extends core::Object {
+abstract class MethodAnnotation extends core::Object /*hasConstConstructor*/  {
 [@vm.unreachable.metadata=] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:1,getterSelectorId:2]  final field core::int* x;
 }
-abstract class TypedefAnnotation extends core::Object {
+abstract class TypedefAnnotation extends core::Object /*hasConstConstructor*/  {
 [@vm.unreachable.metadata=] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:3,getterSelectorId:4]  final field core::List<core::int*>* list;
 }
-abstract class VarAnnotation extends core::Object {
+abstract class VarAnnotation extends core::Object /*hasConstConstructor*/  {
 }
-abstract class ParametrizedAnnotation<T extends core::Object* = dynamic> extends core::Object {
+abstract class ParametrizedAnnotation<T extends core::Object* = dynamic> extends core::Object /*hasConstConstructor*/  {
 [@vm.unreachable.metadata=] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:5,getterSelectorId:6]  final field self::ParametrizedAnnotation::T* foo;
 }
 abstract class A extends core::Object {
diff --git a/pkg/vm/testcases/transformations/type_flow/transformer/const_prop.dart.expect b/pkg/vm/testcases/transformations/type_flow/transformer/const_prop.dart.expect
index 78eb735e020..4c84b68f268 100644
--- a/pkg/vm/testcases/transformations/type_flow/transformer/const_prop.dart.expect
+++ b/pkg/vm/testcases/transformations/type_flow/transformer/const_prop.dart.expect
@@ -11,7 +11,7 @@ class A extends core::Object {
 [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:2,getterSelectorId:3]  method getBar() → core::String*
     return "bar";
 }
-class B extends core::Object {
+class B extends core::Object /*isEnum*/  {
 [@vm.inferred-type.metadata=dart.core::_Smi (value: 1)] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:6,getterSelectorId:7]  final field core::int* index;
 [@vm.inferred-type.metadata=dart.core::_OneByteString (value: B.b2)] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:8,getterSelectorId:9]  final field core::String* _name;
 [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:4,getterSelectorId:5]  method toString() → core::String*
diff --git a/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_new_class2.dart.expect b/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_new_class2.dart.expect
index 15f83fec371..614926714bb 100644
--- a/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_new_class2.dart.expect
+++ b/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_new_class2.dart.expect
@@ -32,7 +32,7 @@ abstract class D extends core::Object {
     : super core::Object::•()
     ;
 }
-abstract class _E&D&C extends self::D implements self::C {
+abstract class _E&D&C extends self::D implements self::C /*isAnonymousMixin,isEliminatedMixin*/  {
   synthetic constructor •() → self::_E&D&C*
     : super self::D::•()
     ;
diff --git a/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_while_processing.dart.expect b/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_while_processing.dart.expect
index 8da19ecb3f8..3390a9121d6 100644
--- a/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_while_processing.dart.expect
+++ b/pkg/vm/testcases/transformations/type_flow/transformer/invalidation_while_processing.dart.expect
@@ -17,7 +17,7 @@ class T2 extends core::Object implements self::I {
     ;
 [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:1,getterSelectorId:2]  method foo() → void {}
 }
-class Point extends core::Object {
+class Point extends core::Object /*hasConstConstructor*/  {
 [@vm.inferred-type.metadata=!] [@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:7,getterSelectorId:8]  final field self::I* x;
   const constructor •([@vm.inferred-type.metadata=!] self::I* x) → self::Point*
     : self::Point::x = x, super core::Object::•()
diff --git a/runtime/vm/kernel_binary.h b/runtime/vm/kernel_binary.h
index 187d3c0c72a..d89e50a92b4 100644
--- a/runtime/vm/kernel_binary.h
+++ b/runtime/vm/kernel_binary.h
@@ -20,7 +20,7 @@ static const uint32_t kMagicProgramFile = 0x90ABCDEFu;
 
 // Both version numbers are inclusive.
 static const uint32_t kMinSupportedKernelFormatVersion = 29;
-static const uint32_t kMaxSupportedKernelFormatVersion = 38;
+static const uint32_t kMaxSupportedKernelFormatVersion = 39;
 
 // Keep in sync with package:kernel/lib/binary/tag.dart
 #define KERNEL_TAG_LIST(V)                                                     \