[cfe] Handle static type of access on Never

Closes #41273

Change-Id: Ia236481ab47033198d7952086cdf5c9c8f5a34b7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142366
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

@@ -1036,23 +1036,10 @@ class TypeInferrerImpl implements TypeInferrer {
 
     if (receiverType is FunctionType && name == callName) {
       return const ObjectAccessTarget.callFunction();
-    }
-
-    Class classNode = receiverType is InterfaceType
-        ? receiverType.classNode
-        : coreTypes.objectClass;
-    Member interfaceMember =
-        _getInterfaceMember(classNode, name, setter, fileOffset);
-    ObjectAccessTarget target;
-    if (interfaceMember != null) {
-      target = new ObjectAccessTarget.interfaceMember(interfaceMember);
-    } else if (receiverType is DynamicType) {
-      target = const ObjectAccessTarget.dynamic();
     } else if (receiverType is NeverType) {
       switch (receiverType.nullability) {
         case Nullability.nonNullable:
-          target = const ObjectAccessTarget.never();
-          break;
+          return const ObjectAccessTarget.never();
         case Nullability.nullable:
         case Nullability.legacy:
           // Never? and Never* are equivalent to Null.
@@ -1066,6 +1053,17 @@ class TypeInferrerImpl implements TypeInferrer {
               fileOffset,
               library.fileUri);
       }
+    }
+    Class classNode = receiverType is InterfaceType
+        ? receiverType.classNode
+        : coreTypes.objectClass;
+    Member interfaceMember =
+        _getInterfaceMember(classNode, name, setter, fileOffset);
+    ObjectAccessTarget target;
+    if (interfaceMember != null) {
+      target = new ObjectAccessTarget.interfaceMember(interfaceMember);
+    } else if (receiverType is DynamicType) {
+      target = const ObjectAccessTarget.dynamic();
     } else if (receiverType is InvalidType) {
       target = const ObjectAccessTarget.invalid();
     } else if (receiverType is InterfaceType &&
@@ -1940,6 +1938,10 @@ class TypeInferrerImpl implements TypeInferrer {
     Member equalsMember =
         findInterfaceMember(variable.type, equalsName, variable.fileOffset)
             .member;
+    // Ensure operator == member even for `Never`.
+    equalsMember ??= findInterfaceMember(const DynamicType(), equalsName, -1,
+            instrumented: false)
+        .member;
     return new NullAwareGuard(
         variable, variable.fileOffset, equalsMember, this);
   }
@@ -2736,7 +2738,7 @@ class TypeInferrerImpl implements TypeInferrer {
         isImplicitCall: isImplicitCall);
     assert(name != equalsName);
     return createNullAwareExpressionInferenceResult(
-        result.inferredType,
+        const NeverType(Nullability.nonNullable),
         result.applyResult(new MethodInvocation(receiver, name, arguments)
           ..fileOffset = fileOffset),
         nullAwareGuards);

pkg/front_end/test/spell_checking_list_code.txt

@@ -689,6 +689,7 @@ nulls
 o
 oauth
 obj
+obligated
 observatory
 observe
 obstruct

pkg/front_end/testcases/nnbd/issue41210a/issue41210_lib1.dart.strong.transformed.expect

@@ -0,0 +1,63 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{self::C::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210a/issue41210_lib1.dart.weak.transformed.expect

@@ -0,0 +1,63 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{self::C::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210b.dart.strong.transformed.expect

@@ -0,0 +1,62 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210b_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210b_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract member-signature method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method() → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{iss::A::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210b_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210b_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210b.dart.weak.transformed.expect

@@ -0,0 +1,62 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210b_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210b_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract member-signature method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method() → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{iss::A::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210b_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210b_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41273.dart

@@ -0,0 +1,32 @@
+// 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.
+
+void test(var x) {
+  if (x is Never) {
+    Never n1 = x.toString();
+    Never n2 = x.runtimeType;
+    Never n3 = x.someGetter;
+    Never n4 = x.someMethod();
+    Never n5 = x + x;
+    Never n6 = x[x];
+    Never n7 = x();
+    Never n8 = x.runtimeType();
+    Never n9 = x.toString;
+    x.runtimeType = Object;
+    x.toString = () => '';
+    var v1 = x.toString();
+    var v2 = x.runtimeType;
+    var v3 = x.someGetter;
+    var v4 = x.someMethod();
+    var v5 = x + x;
+    var v6 = x[x];
+    var v7 = x();
+    var v8 = x.runtimeType();
+    var v9 = x.toString;
+  }
+}
+
+main() {
+  test(null);
+}

pkg/front_end/testcases/nnbd/issue41273.dart.outline.expect

@@ -0,0 +1,7 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+
+static method test(dynamic x) → void
+  ;
+static method main() → dynamic
+  ;

pkg/front_end/testcases/nnbd/issue41273.dart.strong.expect

@@ -0,0 +1,31 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → void {
+  if(x is{ForNonNullableByDefault} Never) {
+    Never n1 = x{Never}.toString();
+    Never n2 = x{Never}.runtimeType;
+    Never n3 = x{Never}.someGetter;
+    Never n4 = x{Never}.someMethod();
+    Never n5 = x{Never}.+(x{Never});
+    Never n6 = x{Never}.[](x{Never});
+    Never n7 = x{Never}.call();
+    Never n8 = x{Never}.runtimeType();
+    Never n9 = x{Never}.toString;
+    x{Never}.runtimeType = core::Object;
+    x{Never}.toString = () → core::String => "";
+    Never v1 = x{Never}.toString();
+    Never v2 = x{Never}.runtimeType;
+    Never v3 = x{Never}.someGetter;
+    Never v4 = x{Never}.someMethod();
+    Never v5 = x{Never}.+(x{Never});
+    Never v6 = x{Never}.[](x{Never});
+    Never v7 = x{Never}.call();
+    Never v8 = x{Never}.runtimeType();
+    Never v9 = x{Never}.toString;
+  }
+}
+static method main() → dynamic {
+  self::test(null);
+}

pkg/front_end/testcases/nnbd/issue41273.dart.strong.transformed.expect

@@ -0,0 +1,31 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → void {
+  if(x is{ForNonNullableByDefault} Never) {
+    Never n1 = x{Never}.toString();
+    Never n2 = x{Never}.runtimeType;
+    Never n3 = x{Never}.someGetter;
+    Never n4 = x{Never}.someMethod();
+    Never n5 = x{Never}.+(x{Never});
+    Never n6 = x{Never}.[](x{Never});
+    Never n7 = x{Never}.call();
+    Never n8 = x{Never}.runtimeType();
+    Never n9 = x{Never}.toString;
+    x{Never}.runtimeType = core::Object;
+    x{Never}.toString = () → core::String => "";
+    Never v1 = x{Never}.toString();
+    Never v2 = x{Never}.runtimeType;
+    Never v3 = x{Never}.someGetter;
+    Never v4 = x{Never}.someMethod();
+    Never v5 = x{Never}.+(x{Never});
+    Never v6 = x{Never}.[](x{Never});
+    Never v7 = x{Never}.call();
+    Never v8 = x{Never}.runtimeType();
+    Never v9 = x{Never}.toString;
+  }
+}
+static method main() → dynamic {
+  self::test(null);
+}

pkg/front_end/testcases/nnbd/issue41273.dart.weak.expect

@@ -0,0 +1,31 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → void {
+  if(x is{ForNonNullableByDefault} Never) {
+    Never n1 = x{Never}.toString();
+    Never n2 = x{Never}.runtimeType;
+    Never n3 = x{Never}.someGetter;
+    Never n4 = x{Never}.someMethod();
+    Never n5 = x{Never}.+(x{Never});
+    Never n6 = x{Never}.[](x{Never});
+    Never n7 = x{Never}.call();
+    Never n8 = x{Never}.runtimeType();
+    Never n9 = x{Never}.toString;
+    x{Never}.runtimeType = core::Object;
+    x{Never}.toString = () → core::String => "";
+    Never v1 = x{Never}.toString();
+    Never v2 = x{Never}.runtimeType;
+    Never v3 = x{Never}.someGetter;
+    Never v4 = x{Never}.someMethod();
+    Never v5 = x{Never}.+(x{Never});
+    Never v6 = x{Never}.[](x{Never});
+    Never v7 = x{Never}.call();
+    Never v8 = x{Never}.runtimeType();
+    Never v9 = x{Never}.toString;
+  }
+}
+static method main() → dynamic {
+  self::test(null);
+}

pkg/front_end/testcases/nnbd/issue41273.dart.weak.transformed.expect

@@ -0,0 +1,31 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → void {
+  if(x is{ForNonNullableByDefault} Never) {
+    Never n1 = x{Never}.toString();
+    Never n2 = x{Never}.runtimeType;
+    Never n3 = x{Never}.someGetter;
+    Never n4 = x{Never}.someMethod();
+    Never n5 = x{Never}.+(x{Never});
+    Never n6 = x{Never}.[](x{Never});
+    Never n7 = x{Never}.call();
+    Never n8 = x{Never}.runtimeType();
+    Never n9 = x{Never}.toString;
+    x{Never}.runtimeType = core::Object;
+    x{Never}.toString = () → core::String => "";
+    Never v1 = x{Never}.toString();
+    Never v2 = x{Never}.runtimeType;
+    Never v3 = x{Never}.someGetter;
+    Never v4 = x{Never}.someMethod();
+    Never v5 = x{Never}.+(x{Never});
+    Never v6 = x{Never}.[](x{Never});
+    Never v7 = x{Never}.call();
+    Never v8 = x{Never}.runtimeType();
+    Never v9 = x{Never}.toString;
+  }
+}
+static method main() → dynamic {
+  self::test(null);
+}

pkg/front_end/testcases/nnbd/never_receiver.dart

@@ -21,6 +21,12 @@ foo(Never x, Never? y) {
   y?.[42]; // Not an error.
   y?.[42] = 42; // Not an error.
 
+  x?.foo(); // Warning.
+  x?.bar; // Warning.
+  x?.baz = 42; // Warning.
+  x?.[42]; // Warning.
+  x?.[42] = 42; // Warning.
+
   y.foo(); // Error.
   y.bar; // Error.
   y.baz = 42; // Error.

pkg/front_end/testcases/nnbd/never_receiver.dart.strong.expect

@@ -2,69 +2,89 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:24:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.foo(); // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:25:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.bar; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:26:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.baz = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:27:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42]; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:28:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42] = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'foo'.
 //   y.foo(); // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'call'.
 //   y(); // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]' operator.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]=' operator.
 //   y[42] = 42; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
 //   y[42] = 42; // Error.
 //    ^
 //
@@ -82,55 +102,60 @@ static method foo(Never x, Never? y) → dynamic {
   x.[]=(42, 42);
   x = x.+(1);
   x = x.+(1);
-  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{dynamic} null : #t1{Never}.foo();
+  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{core::Null?} null : #t1{Never}.foo();
   let final Never? #t2 = y in #t2.{core::Object::==}(null) ?{core::Null?} null : #t2{Never}.bar;
   let final Never? #t3 = y in #t3.{core::Object::==}(null) ?{core::int?} null : #t3{Never}.baz = 42;
-  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{dynamic} null : #t4{Never}.call();
+  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{core::Null?} null : #t4{Never}.call();
   let final Never? #t5 = y in #t5.{core::Object::==}(null) ?{core::Null?} null : #t5{Never}.[](42);
   let final Never? #t6 = y in #t6.{core::Object::==}(null) ?{core::int?} null : #t6{Never}.[]=(42, 42);
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+  let final Never #t7 = x in #t7.{core::Object::==}(null) ?{core::Null?} null : #t7.foo();
+  let final Never #t8 = x in #t8.{core::Object::==}(null) ?{core::Null?} null : #t8.bar;
+  let final Never #t9 = x in #t9.{core::Object::==}(null) ?{core::int?} null : #t9.baz = 42;
+  let final Never #t10 = x in #t10.{core::Object::==}(null) ?{core::Null?} null : #t10.[](42);
+  let final Never #t11 = x in #t11.{core::Object::==}(null) ?{core::int?} null : #t11.[]=(42, 42);
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'foo'.
   y.foo(); // Error.
     ^^^";
-  let final<BottomType> #t7 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.bar; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
   y.bar; // Error.
     ^^^";
-  let final<BottomType> #t8 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t13 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.baz = 42; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
   y.baz = 42; // Error.
     ^^^";
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'call'.
   y(); // Error.
    ^";
-  y = (let final<BottomType> #t9 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t14 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y++; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y++; // Error.
    ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  y = (let final<BottomType> #t10 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t15 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y += 1; // Error.
-    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y += 1; // Error.
     ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  let final<BottomType> #t11 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t16 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
   y[42]; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]' operator.
   y[42]; // Error.
    ^";
-  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t17 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
   y[42] = 42; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]=' operator.
   y[42] = 42; // Error.
    ^";

pkg/front_end/testcases/nnbd/never_receiver.dart.strong.transformed.expect

@@ -2,69 +2,89 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:24:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.foo(); // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:25:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.bar; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:26:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.baz = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:27:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42]; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:28:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42] = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'foo'.
 //   y.foo(); // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'call'.
 //   y(); // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]' operator.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]=' operator.
 //   y[42] = 42; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
 //   y[42] = 42; // Error.
 //    ^
 //
@@ -82,55 +102,60 @@ static method foo(Never x, Never? y) → dynamic {
   x.[]=(42, 42);
   x = x.+(1);
   x = x.+(1);
-  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{dynamic} null : #t1{Never}.foo();
+  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{core::Null?} null : #t1{Never}.foo();
   let final Never? #t2 = y in #t2.{core::Object::==}(null) ?{core::Null?} null : #t2{Never}.bar;
   let final Never? #t3 = y in #t3.{core::Object::==}(null) ?{core::int?} null : #t3{Never}.baz = 42;
-  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{dynamic} null : #t4{Never}.call();
+  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{core::Null?} null : #t4{Never}.call();
   let final Never? #t5 = y in #t5.{core::Object::==}(null) ?{core::Null?} null : #t5{Never}.[](42);
   let final Never? #t6 = y in #t6.{core::Object::==}(null) ?{core::int?} null : #t6{Never}.[]=(42, 42);
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+  let final Never #t7 = x in #t7.{core::Object::==}(null) ?{core::Null?} null : #t7.foo();
+  let final Never #t8 = x in #t8.{core::Object::==}(null) ?{core::Null?} null : #t8.bar;
+  let final Never #t9 = x in #t9.{core::Object::==}(null) ?{core::int?} null : #t9.baz = 42;
+  let final Never #t10 = x in #t10.{core::Object::==}(null) ?{core::Null?} null : #t10.[](42);
+  let final Never #t11 = x in #t11.{core::Object::==}(null) ?{core::int?} null : #t11.[]=(42, 42);
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'foo'.
   y.foo(); // Error.
     ^^^";
-  let final<BottomType> #t7 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.bar; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
   y.bar; // Error.
     ^^^";
-  let final<BottomType> #t8 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t13 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.baz = 42; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
   y.baz = 42; // Error.
     ^^^";
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'call'.
   y(); // Error.
    ^";
-  y = (let final<BottomType> #t9 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t14 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y++; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y++; // Error.
    ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  y = (let final<BottomType> #t10 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t15 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y += 1; // Error.
-    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y += 1; // Error.
     ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  let final<BottomType> #t11 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t16 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
   y[42]; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]' operator.
   y[42]; // Error.
    ^";
-  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t17 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
   y[42] = 42; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]=' operator.
   y[42] = 42; // Error.
    ^";

pkg/front_end/testcases/nnbd/never_receiver.dart.weak.expect

@@ -2,69 +2,89 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:24:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.foo(); // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:25:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.bar; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:26:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.baz = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:27:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42]; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:28:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42] = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'foo'.
 //   y.foo(); // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'call'.
 //   y(); // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]' operator.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]=' operator.
 //   y[42] = 42; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
 //   y[42] = 42; // Error.
 //    ^
 //
@@ -82,55 +102,60 @@ static method foo(Never x, Never? y) → dynamic {
   x.[]=(42, 42);
   x = x.+(1);
   x = x.+(1);
-  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{dynamic} null : #t1{Never}.foo();
+  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{core::Null?} null : #t1{Never}.foo();
   let final Never? #t2 = y in #t2.{core::Object::==}(null) ?{core::Null?} null : #t2{Never}.bar;
   let final Never? #t3 = y in #t3.{core::Object::==}(null) ?{core::int?} null : #t3{Never}.baz = 42;
-  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{dynamic} null : #t4{Never}.call();
+  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{core::Null?} null : #t4{Never}.call();
   let final Never? #t5 = y in #t5.{core::Object::==}(null) ?{core::Null?} null : #t5{Never}.[](42);
   let final Never? #t6 = y in #t6.{core::Object::==}(null) ?{core::int?} null : #t6{Never}.[]=(42, 42);
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+  let final Never #t7 = x in #t7.{core::Object::==}(null) ?{core::Null?} null : #t7.foo();
+  let final Never #t8 = x in #t8.{core::Object::==}(null) ?{core::Null?} null : #t8.bar;
+  let final Never #t9 = x in #t9.{core::Object::==}(null) ?{core::int?} null : #t9.baz = 42;
+  let final Never #t10 = x in #t10.{core::Object::==}(null) ?{core::Null?} null : #t10.[](42);
+  let final Never #t11 = x in #t11.{core::Object::==}(null) ?{core::int?} null : #t11.[]=(42, 42);
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'foo'.
   y.foo(); // Error.
     ^^^";
-  let final<BottomType> #t7 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.bar; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
   y.bar; // Error.
     ^^^";
-  let final<BottomType> #t8 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t13 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.baz = 42; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
   y.baz = 42; // Error.
     ^^^";
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'call'.
   y(); // Error.
    ^";
-  y = (let final<BottomType> #t9 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t14 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y++; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y++; // Error.
    ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  y = (let final<BottomType> #t10 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t15 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y += 1; // Error.
-    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y += 1; // Error.
     ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  let final<BottomType> #t11 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t16 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
   y[42]; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]' operator.
   y[42]; // Error.
    ^";
-  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t17 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
   y[42] = 42; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]=' operator.
   y[42] = 42; // Error.
    ^";

pkg/front_end/testcases/nnbd/never_receiver.dart.weak.transformed.expect

@@ -2,69 +2,89 @@ library /*isNonNullableByDefault*/;
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:24:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.foo(); // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:25:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.bar; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:26:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.baz = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:27:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42]; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:28:3: Warning: Operand of null-aware operation '?.' has type 'Never' which excludes null.
+//   x?.[42] = 42; // Warning.
+//   ^
+//
+// pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'foo'.
 //   y.foo(); // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.bar; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 // Try accessing using ?. instead.
 //   y.baz = 42; // Error.
 //     ^^^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 // Try correcting the name to the name of an existing method, or defining a method named 'call'.
 //   y(); // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y++; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '+' operator.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
 //   y += 1; // Error.
 //     ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]' operator.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
 //   y[42]; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 // Try correcting the operator to an existing operator, or defining a '[]=' operator.
 //   y[42] = 42; // Error.
 //    ^
 //
-// pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+// pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
 //   y[42] = 42; // Error.
 //    ^
 //
@@ -82,55 +102,60 @@ static method foo(Never x, Never? y) → dynamic {
   x.[]=(42, 42);
   x = x.+(1);
   x = x.+(1);
-  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{dynamic} null : #t1{Never}.foo();
+  let final Never? #t1 = y in #t1.{core::Object::==}(null) ?{core::Null?} null : #t1{Never}.foo();
   let final Never? #t2 = y in #t2.{core::Object::==}(null) ?{core::Null?} null : #t2{Never}.bar;
   let final Never? #t3 = y in #t3.{core::Object::==}(null) ?{core::int?} null : #t3{Never}.baz = 42;
-  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{dynamic} null : #t4{Never}.call();
+  let final Never? #t4 = y in #t4.{core::Object::==}(null) ?{core::Null?} null : #t4{Never}.call();
   let final Never? #t5 = y in #t5.{core::Object::==}(null) ?{core::Null?} null : #t5{Never}.[](42);
   let final Never? #t6 = y in #t6.{core::Object::==}(null) ?{core::int?} null : #t6{Never}.[]=(42, 42);
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:24:5: Error: The method 'foo' isn't defined for the class 'Never'.
+  let final Never #t7 = x in #t7.{core::Object::==}(null) ?{core::Null?} null : #t7.foo();
+  let final Never #t8 = x in #t8.{core::Object::==}(null) ?{core::Null?} null : #t8.bar;
+  let final Never #t9 = x in #t9.{core::Object::==}(null) ?{core::int?} null : #t9.baz = 42;
+  let final Never #t10 = x in #t10.{core::Object::==}(null) ?{core::Null?} null : #t10.[](42);
+  let final Never #t11 = x in #t11.{core::Object::==}(null) ?{core::int?} null : #t11.[]=(42, 42);
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:5: Error: The method 'foo' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'foo'.
   y.foo(); // Error.
     ^^^";
-  let final<BottomType> #t7 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: Property 'bar' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.bar; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:25:5: Error: The getter 'bar' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:5: Error: The getter 'bar' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing getter, or defining a getter or field named 'bar'.
   y.bar; // Error.
     ^^^";
-  let final<BottomType> #t8 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
+  let final<BottomType> #t13 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: Property 'baz' cannot be accessed on 'Never' because it is potentially null.
 Try accessing using ?. instead.
   y.baz = 42; // Error.
-    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:26:5: Error: The setter 'baz' isn't defined for the class 'Never'.
+    ^^^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:32:5: Error: The setter 'baz' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing setter, or defining a setter or field named 'baz'.
   y.baz = 42; // Error.
     ^^^";
-  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:27:4: Error: The method 'call' isn't defined for the class 'Never'.
+  invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:33:4: Error: The method 'call' isn't defined for the class 'Never'.
 Try correcting the name to the name of an existing method, or defining a method named 'call'.
   y(); // Error.
    ^";
-  y = (let final<BottomType> #t9 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t14 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y++; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:28:4: Error: The operator '+' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:34:4: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y++; // Error.
    ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  y = (let final<BottomType> #t10 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
+  y = (let final<BottomType> #t15 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: Operator '+' cannot be called on 'Never' because it is potentially null.
   y += 1; // Error.
-    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:29:5: Error: The operator '+' isn't defined for the class 'Never'.
+    ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:35:5: Error: The operator '+' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '+' operator.
   y += 1; // Error.
     ^") as{TypeError,ForDynamic,ForNonNullableByDefault} Never?;
-  let final<BottomType> #t11 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t16 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: Operator '[]' cannot be called on 'Never' because it is potentially null.
   y[42]; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:30:4: Error: The operator '[]' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:36:4: Error: The operator '[]' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]' operator.
   y[42]; // Error.
    ^";
-  let final<BottomType> #t12 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
+  let final<BottomType> #t17 = invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: Operator '[]=' cannot be called on 'Never' because it is potentially null.
   y[42] = 42; // Error.
-   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:31:4: Error: The operator '[]=' isn't defined for the class 'Never'.
+   ^" in invalid-expression "pkg/front_end/testcases/nnbd/never_receiver.dart:37:4: Error: The operator '[]=' isn't defined for the class 'Never'.
 Try correcting the operator to an existing operator, or defining a '[]=' operator.
   y[42] = 42; // Error.
    ^";

pkg/front_end/testcases/outline.status

@@ -40,8 +40,6 @@ inference/mixin_inference_outwards_4: TypeCheckError
 inference/mixin_inference_unification_1: TypeCheckError
 inference/mixin_inference_unification_2: TypeCheckError
 nnbd/inheritance_from_opt_in: TypeCheckError
-nnbd/issue41210a/issue41210: TypeCheckError
-nnbd/issue41210b: TypeCheckError
 nnbd/messages_with_types_opt_in: TypeCheckError
 nnbd/messages_with_types_opt_out: TypeCheckError
 nnbd/never_opt_out: TypeCheckError

pkg/front_end/testcases/strong.status

@@ -167,8 +167,6 @@ instantiate_to_bound/non_simple_class_parametrized_typedef_cycle: RuntimeError #
 instantiate_to_bound/non_simple_generic_function_in_bound_regress: RuntimeError # Expected
 nnbd/inheritance_from_opt_in: TypeCheckError
 nnbd/issue41180: RuntimeError # Strong mode runtime checking fails due to mixed strong mode.
-nnbd/issue41210a/issue41210: TypeCheckError
-nnbd/issue41210b: TypeCheckError
 nnbd/messages_with_types_opt_in: TypeCheckError
 nnbd/messages_with_types_opt_out: TypeCheckError
 nnbd/never_opt_out: TypeCheckError

pkg/front_end/testcases/text_serialization.status

@@ -1331,8 +1331,9 @@ nnbd/issue41102: TextSerializationFailure
 nnbd/issue41103: TextSerializationFailure
 nnbd/issue41156: TextSerializationFailure
 nnbd/issue41180: TextSerializationFailure
-nnbd/issue41210a/issue41210: TypeCheckError
-nnbd/issue41210b: TypeCheckError
+nnbd/issue41210a/issue41210: TextSerializationFailure
+nnbd/issue41210b: TextSerializationFailure
+nnbd/issue41273: TextSerializationFailure
 nnbd/late: TextSerializationFailure
 nnbd/later: TextSerializationFailure
 nnbd/lhs_of_if_null: TextSerializationFailure

pkg/front_end/testcases/weak.status

@@ -59,8 +59,6 @@ general_nnbd_opt_out/type_variable_bound_access: TypeCheckError
 general_nnbd_opt_out/unsound_promotion: TypeCheckError
 general_nnbd_opt_out/void_methods: RuntimeError
 nnbd/inheritance_from_opt_in: TypeCheckError
-nnbd/issue41210a/issue41210: TypeCheckError
-nnbd/issue41210b: TypeCheckError
 nnbd/messages_with_types_opt_in: TypeCheckError
 nnbd/messages_with_types_opt_out: TypeCheckError
 nnbd/never_opt_out: TypeCheckError

pkg/kernel/lib/naive_type_checker.dart

@@ -131,6 +131,13 @@ ${ownType} is not a subtype of ${superType}
   /// but it additionally accounts for parameter covariance.
   String _checkFunctionOverride(
       Class host, Member ownMember, Member superMember) {
+    if (ownMember is Procedure &&
+        (ownMember.isMemberSignature ||
+            (ownMember.isForwardingStub && !ownMember.isForwardingSemiStub))) {
+      // Synthesized members are not obligated to override super members.
+      return null;
+    }
+
     final FunctionNode ownFunction = ownMember.function;
     final FunctionNode superFunction = superMember.function;
     Substitution ownSubstitution = _makeSubstitutionForMember(host, ownMember);