diff --git a/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart b/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
index 72487895a9c..779de84b6a4 100644
--- a/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
+++ b/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
@@ -7814,6 +7814,46 @@ Message _withArgumentsNonAsciiWhitespace(int codePoint) {
       arguments: {'unicode': codePoint});
 }
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        String
+            name)> templateNonAugmentationClassMemberConflict = const Template<
+        Message Function(String name)>(
+    problemMessageTemplate:
+        r"""Member '#name' conflicts with an existing member of the same name in the augmented class.""",
+    correctionMessageTemplate:
+        r"""Try changing the name to an existing member or adding an 'augment' modifier.""",
+    withArguments: _withArgumentsNonAugmentationClassMemberConflict);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeNonAugmentationClassMemberConflict =
+    const Code<Message Function(String name)>(
+  "NonAugmentationClassMemberConflict",
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsNonAugmentationClassMemberConflict(String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeNonAugmentationClassMemberConflict,
+      problemMessage:
+          """Member '${name}' conflicts with an existing member of the same name in the augmented class.""",
+      correctionMessage: """Try changing the name to an existing member or adding an 'augment' modifier.""",
+      arguments: {'name': name});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeNonAugmentationClassMemberConflictCause =
+    messageNonAugmentationClassMemberConflictCause;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageNonAugmentationClassMemberConflictCause =
+    const MessageCode("NonAugmentationClassMemberConflictCause",
+        severity: Severity.context,
+        problemMessage: r"""This is the existing member.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeNonConstConstructor = messageNonConstConstructor;
 
@@ -10394,6 +10434,35 @@ const MessageCode messageUnexpectedTokens = const MessageCode(
     index: 123,
     problemMessage: r"""Unexpected tokens.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        String
+            name)> templateUnmatchedAugmentationClassMember = const Template<
+        Message Function(String name)>(
+    problemMessageTemplate:
+        r"""Augmentation member '#name' doesn't match a member in the augmented class.""",
+    correctionMessageTemplate:
+        r"""Try changing the name to an existing member or removing the 'augment' modifier.""",
+    withArguments: _withArgumentsUnmatchedAugmentationClassMember);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)> codeUnmatchedAugmentationClassMember =
+    const Code<Message Function(String name)>(
+  "UnmatchedAugmentationClassMember",
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsUnmatchedAugmentationClassMember(String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeUnmatchedAugmentationClassMember,
+      problemMessage:
+          """Augmentation member '${name}' doesn't match a member in the augmented class.""",
+      correctionMessage: """Try changing the name to an existing member or removing the 'augment' modifier.""",
+      arguments: {'name': name});
+}
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(String string, Token token)>
     templateUnmatchedToken =
diff --git a/pkg/front_end/lib/src/fasta/kernel/hierarchy/members_node.dart b/pkg/front_end/lib/src/fasta/kernel/hierarchy/members_node.dart
index f93f47eda0a..e4a28398142 100644
--- a/pkg/front_end/lib/src/fasta/kernel/hierarchy/members_node.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/hierarchy/members_node.dart
@@ -1374,7 +1374,7 @@ class ClassMembersNodeBuilder {
         if (classBuilder is SourceClassBuilder && !declaredMember.isStatic) {
           assert(
               declaredMember.isSourceDeclaration &&
-                  declaredMember.classBuilder == classBuilder,
+                  declaredMember.classBuilder.origin == classBuilder,
               "Only declared members can override: ${declaredMember}");
           hasDeclaredMembers = true;
           if (declaredMember.isProperty) {
diff --git a/pkg/front_end/lib/src/fasta/scope.dart b/pkg/front_end/lib/src/fasta/scope.dart
index ef9097399e7..ab0037c5054 100644
--- a/pkg/front_end/lib/src/fasta/scope.dart
+++ b/pkg/front_end/lib/src/fasta/scope.dart
@@ -809,6 +809,15 @@ mixin ErroneousMemberBuilderMixin implements SourceMemberBuilder {
   @override
   bool get isConflictingSetter => false;
 
+  @override
+  bool get isConflictingAugmentationMember => false;
+
+  @override
+  void set isConflictingAugmentationMember(bool value) {
+    throw new UnsupportedError(
+        'AmbiguousMemberBuilder.isConflictingAugmentationMember=');
+  }
+
   @override
   void set parent(Builder? value) {
     throw new UnsupportedError('AmbiguousMemberBuilder.parent=');
@@ -861,6 +870,11 @@ mixin ErroneousMemberBuilderMixin implements SourceMemberBuilder {
       SourceLibraryBuilder library, TypeEnvironment typeEnvironment) {
     assert(false, "Unexpected call to $runtimeType.checkVariance.");
   }
+
+  @override
+  bool get isAugmentation {
+    throw new UnsupportedError('AmbiguousMemberBuilder.isAugmentation');
+  }
 }
 
 class AmbiguousMemberBuilder extends AmbiguousBuilder
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 102db7f3c3a..f24406dd539 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
@@ -158,15 +158,17 @@ class SourceClassBuilder extends ClassBuilderImpl
     void buildBuilders(String name, Builder? declaration) {
       while (declaration != null) {
         if (declaration.parent != this) {
-          if (fileUri != declaration.parent?.fileUri) {
-            unexpected("$fileUri", "${declaration.parent?.fileUri}", charOffset,
-                fileUri);
-          } else {
-            unexpected(
-                fullNameForErrors,
-                declaration.parent?.fullNameForErrors ?? '',
-                charOffset,
-                fileUri);
+          if (declaration.parent?.origin != this) {
+            if (fileUri != declaration.parent?.fileUri) {
+              unexpected("$fileUri", "${declaration.parent?.fileUri}",
+                  charOffset, fileUri);
+            } else {
+              unexpected(
+                  fullNameForErrors,
+                  declaration.parent?.fullNameForErrors ?? '',
+                  charOffset,
+                  fileUri);
+            }
           }
         } else if (declaration is SourceMemberBuilder) {
           SourceMemberBuilder memberBuilder = declaration;
@@ -175,7 +177,8 @@ class SourceClassBuilder extends ClassBuilderImpl
             member.parent = cls;
             if (!memberBuilder.isPatch &&
                 !memberBuilder.isDuplicate &&
-                !memberBuilder.isConflictingSetter) {
+                !memberBuilder.isConflictingSetter &&
+                !memberBuilder.isConflictingAugmentationMember) {
               if (member is Procedure) {
                 cls.addProcedure(member);
               } else if (member is Field) {
@@ -602,21 +605,71 @@ class SourceClassBuilder extends ClassBuilderImpl
     if (patch is SourceClassBuilder) {
       patch.actualOrigin = this;
       (_patches ??= []).add(patch);
-      // TODO(ahe): Complain if `patch.supertype` isn't null.
-      scope.forEachLocalMember((String name, Builder member) {
-        Builder? memberPatch =
-            patch.scope.lookupLocalMember(name, setter: false);
-        if (memberPatch != null) {
-          member.applyPatch(memberPatch);
+
+      void applyAugmentation(String name, SourceMemberBuilder patchMember,
+          {required bool setter}) {
+        Builder? originMember = scope.lookupLocalMember(name, setter: setter);
+        if (patch.isAugmentation) {
+          if (originMember != null) {
+            if (patchMember.isAugmentation) {
+              originMember.applyPatch(patchMember);
+            } else {
+              patchMember.isConflictingAugmentationMember = true;
+              library.addProblem(
+                  templateNonAugmentationClassMemberConflict
+                      .withArguments(name),
+                  patchMember.charOffset,
+                  name.length,
+                  patchMember.fileUri,
+                  context: [
+                    messageNonAugmentationClassMemberConflictCause.withLocation(
+                        originMember.fileUri!,
+                        originMember.charOffset,
+                        name.length)
+                  ]);
+            }
+          } else {
+            if (patchMember.isAugmentation) {
+              library.addProblem(
+                  templateUnmatchedAugmentationClassMember.withArguments(name),
+                  patchMember.charOffset,
+                  name.length,
+                  patchMember.fileUri);
+            } else {
+              scope.addLocalMember(name, patchMember, setter: setter);
+            }
+          }
+        } else {
+          if (originMember != null) {
+            // Patch class implicitly assume matching members are patch
+            // members.
+            originMember.applyPatch(patchMember);
+          } else {
+            // Members injected into patch are not part of the origin scope.
+          }
+        }
+      }
+
+      patch.scope.forEachLocalMember((String name, Builder patchMember) {
+        if (patchMember is SourceMemberBuilder) {
+          applyAugmentation(name, patchMember, setter: false);
+        } else {
+          assert(false,
+              "Unexpected member ${patchMember} (${patchMember.runtimeType})");
         }
       });
-      scope.forEachLocalSetter((String name, Builder member) {
-        Builder? memberPatch =
-            patch.scope.lookupLocalMember(name, setter: true);
-        if (memberPatch != null) {
-          member.applyPatch(memberPatch);
+
+      patch.scope.forEachLocalSetter((String name, Builder patchMember) {
+        if (patchMember is SourceMemberBuilder) {
+          applyAugmentation(name, patchMember, setter: true);
+        } else {
+          assert(false,
+              "Unexpected member ${patchMember} (${patchMember.runtimeType})");
         }
       });
+
+      // TODO(johnniwinther): Should we support constructor augmentation?
+      // Currently the syntax doesn't allow it.
       constructors.local.forEach((String name, Builder member) {
         Builder? memberPatch = patch.constructors.local[name];
         if (memberPatch != null) {
diff --git a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
index bb1a2546f1e..ce1548cc5d1 100644
--- a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
@@ -798,7 +798,10 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       }
     } else {
       resolvedUri = resolve(this.importUri, uri, uriOffset);
-      builder = loader.read(resolvedUri, uriOffset, accessor: this);
+      builder = loader.read(resolvedUri, uriOffset,
+          origin: isAugmentationImport ? this : null,
+          accessor: this,
+          isAugmentation: isAugmentationImport);
     }
 
     imports.add(new Import(
diff --git a/pkg/front_end/lib/src/fasta/source/source_loader.dart b/pkg/front_end/lib/src/fasta/source/source_loader.dart
index 68f2d847c2e..257a4b82465 100644
--- a/pkg/front_end/lib/src/fasta/source/source_loader.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_loader.dart
@@ -321,7 +321,8 @@ class SourceLoader extends Loader {
       required LanguageVersion packageLanguageVersion,
       SourceLibraryBuilder? origin,
       Library? referencesFrom,
-      bool? referenceIsPartOwner}) {
+      bool? referenceIsPartOwner,
+      bool isAugmentation: false}) {
     return new SourceLibraryBuilder(
         importUri: importUri,
         fileUri: fileUri,
@@ -334,7 +335,7 @@ class SourceLoader extends Loader {
         isUnsupported: origin?.library.isUnsupported ??
             importUri.isScheme('dart') &&
                 !target.uriTranslator.isLibrarySupported(importUri.path),
-        isAugmentation: false);
+        isAugmentation: isAugmentation);
   }
 
   /// Return `"true"` if the [dottedName] is a 'dart.library.*' qualifier for a
@@ -364,7 +365,8 @@ class SourceLoader extends Loader {
       Uri? fileUri,
       SourceLibraryBuilder? origin,
       Library? referencesFrom,
-      bool? referenceIsPartOwner) {
+      bool? referenceIsPartOwner,
+      bool isAugmentation) {
     if (fileUri != null &&
         (fileUri.isScheme("dart") ||
             fileUri.isScheme("package") ||
@@ -444,7 +446,8 @@ class SourceLoader extends Loader {
         packageLanguageVersion: packageLanguageVersion,
         origin: origin,
         referencesFrom: referencesFrom,
-        referenceIsPartOwner: referenceIsPartOwner);
+        referenceIsPartOwner: referenceIsPartOwner,
+        isAugmentation: isAugmentation);
     if (packageLanguageVersionProblem != null) {
       libraryBuilder.addPostponedProblem(
           packageLanguageVersionProblem, 0, noLength, libraryBuilder.fileUri);
@@ -556,12 +559,14 @@ class SourceLoader extends Loader {
       required LibraryBuilder accessor,
       LibraryBuilder? origin,
       Library? referencesFrom,
-      bool? referenceIsPartOwner}) {
+      bool? referenceIsPartOwner,
+      bool isAugmentation: false}) {
     LibraryBuilder libraryBuilder = _read(uri,
         fileUri: fileUri,
         origin: origin,
         referencesFrom: referencesFrom,
-        referenceIsPartOwner: referenceIsPartOwner);
+        referenceIsPartOwner: referenceIsPartOwner,
+        isAugmentation: isAugmentation);
     libraryBuilder.recordAccess(charOffset, noLength, accessor.fileUri);
     if (!_hasLibraryAccess(imported: uri, importer: accessor.importUri) &&
         !accessor.isPatch) {
@@ -617,7 +622,8 @@ class SourceLoader extends Loader {
       {Uri? fileUri,
       LibraryBuilder? origin,
       Library? referencesFrom,
-      bool? referenceIsPartOwner}) {
+      bool? referenceIsPartOwner,
+      bool isAugmentation: false}) {
     LibraryBuilder? libraryBuilder = _builders[uri];
     if (libraryBuilder == null) {
       if (target.dillTarget.isLoaded) {
@@ -629,7 +635,8 @@ class SourceLoader extends Loader {
             fileUri,
             origin as SourceLibraryBuilder?,
             referencesFrom,
-            referenceIsPartOwner);
+            referenceIsPartOwner,
+            isAugmentation);
       }
       _builders[uri] = libraryBuilder;
     }
diff --git a/pkg/front_end/lib/src/fasta/source/source_member_builder.dart b/pkg/front_end/lib/src/fasta/source/source_member_builder.dart
index fcdfb76baac..f4cf938c1db 100644
--- a/pkg/front_end/lib/src/fasta/source/source_member_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_member_builder.dart
@@ -14,6 +14,7 @@ import '../builder/declaration_builder.dart';
 import '../builder/library_builder.dart';
 import '../builder/member_builder.dart';
 import '../kernel/kernel_helper.dart';
+import '../modifier.dart';
 import '../problems.dart' show unsupported;
 import '../source/source_library_builder.dart';
 import '../type_inference/type_inference_engine.dart'
@@ -42,6 +43,14 @@ abstract class SourceMemberBuilder implements MemberBuilder {
   /// Checks the signature types of this member.
   void checkTypes(
       SourceLibraryBuilder library, TypeEnvironment typeEnvironment);
+
+  /// Returns `true` if this member is an augmentation.
+  bool get isAugmentation;
+
+  /// Returns `true` if this member is a member declared in an augmentation
+  /// library that conflicts with a member in the origin library.
+  bool get isConflictingAugmentationMember;
+  void set isConflictingAugmentationMember(bool value);
 }
 
 mixin SourceMemberBuilderMixin implements SourceMemberBuilder {
@@ -54,6 +63,18 @@ mixin SourceMemberBuilderMixin implements SourceMemberBuilder {
       SourceLibraryBuilder library, void Function(Member, BuiltMemberKind) f) {
     assert(false, "Unexpected call to $runtimeType.buildMembers.");
   }
+
+  @override
+  bool get isAugmentation => false;
+
+  @override
+  bool get isConflictingAugmentationMember => false;
+
+  @override
+  void set isConflictingAugmentationMember(bool value) {
+    assert(false,
+        "Unexpected call to $runtimeType.isConflictingAugmentationMember=");
+  }
 }
 
 abstract class SourceMemberBuilderImpl extends MemberBuilderImpl
@@ -68,6 +89,9 @@ abstract class SourceMemberBuilderImpl extends MemberBuilderImpl
 
   bool get isRedirectingGenerativeConstructor => false;
 
+  @override
+  bool get isAugmentation => modifiers & augmentMask != 0;
+
   bool? _isConflictingSetter;
 
   @override
@@ -81,6 +105,20 @@ abstract class SourceMemberBuilderImpl extends MemberBuilderImpl
     _isConflictingSetter = value;
   }
 
+  bool? _isConflictingAugmentationMember;
+
+  @override
+  bool get isConflictingAugmentationMember {
+    return _isConflictingAugmentationMember ??= false;
+  }
+
+  @override
+  void set isConflictingAugmentationMember(bool value) {
+    assert(_isConflictingAugmentationMember == null,
+        '$this.isConflictingAugmentationMember has already been fixed.');
+    _isConflictingAugmentationMember = value;
+  }
+
   // TODO(johnniwinther): Remove this and create a [ProcedureBuilder] interface.
   @override
   ProcedureKind? get kind => unsupported("kind", charOffset, fileUri);
diff --git a/pkg/front_end/messages.status b/pkg/front_end/messages.status
index b2e67dc1e73..5ff0e553d3e 100644
--- a/pkg/front_end/messages.status
+++ b/pkg/front_end/messages.status
@@ -644,6 +644,8 @@ NonAgnosticConstant/analyzerCode: Fail
 NonAgnosticConstant/example: Fail
 NonAsciiIdentifier/expression: Fail
 NonAsciiIdentifier/part_wrapped_expression: Fail
+NonAugmentationClassMemberConflict/analyzerCode: Fail
+NonAugmentationClassMemberConflict/example: Fail
 NonConstConstructor/example: Fail
 NonConstFactory/example: Fail
 NonInstanceTypeVariableUse/example: Fail
@@ -849,6 +851,8 @@ UndefinedExtensionSetter/analyzerCode: Fail
 UndefinedExtensionSetter/example: Fail
 UnexpectedToken/part_wrapped_script1: Fail
 UnexpectedToken/script1: Fail
+UnmatchedAugmentationClassMember/analyzerCode: Fail
+UnmatchedAugmentationClassMember/example: Fail
 UnmatchedToken/part_wrapped_script1: Fail
 UnmatchedToken/part_wrapped_script3: Fail
 UnmatchedToken/script1: Fail
diff --git a/pkg/front_end/messages.yaml b/pkg/front_end/messages.yaml
index b3403f3e942..8e6f4151b86 100644
--- a/pkg/front_end/messages.yaml
+++ b/pkg/front_end/messages.yaml
@@ -5507,3 +5507,15 @@ EnumImplementerContainsValuesDeclaration:
 MacroClassNotDeclaredMacro:
   problemMessage: "Non-abstract class '#name' implements 'Macro' but isn't declared as a macro class."
   correctionMessage: "Try adding the 'macro' class modifier."
+
+UnmatchedAugmentationClassMember:
+  problemMessage: "Augmentation member '#name' doesn't match a member in the augmented class."
+  correctionMessage: "Try changing the name to an existing member or removing the 'augment' modifier."
+
+NonAugmentationClassMemberConflict:
+  problemMessage: "Member '#name' conflicts with an existing member of the same name in the augmented class."
+  correctionMessage: "Try changing the name to an existing member or adding an 'augment' modifier."
+
+NonAugmentationClassMemberConflictCause:
+  problemMessage: "This is the existing member."
+  severity: CONTEXT
diff --git a/pkg/front_end/test/macro_application/data/pkgs/macro/lib/macro2.dart b/pkg/front_end/test/macro_application/data/pkgs/macro/lib/macro2.dart
index a444cf03953..6173f58be42 100644
--- a/pkg/front_end/test/macro_application/data/pkgs/macro/lib/macro2.dart
+++ b/pkg/front_end/test/macro_application/data/pkgs/macro/lib/macro2.dart
@@ -15,8 +15,10 @@ class Macro2 implements ClassDeclarationsMacro {
   @override
   FutureOr<void> buildDeclarationsForClass(ClassDeclaration clazz,
       ClassMemberDeclarationBuilder builder) {
-    builder.declareInClass(new DeclarationCode.fromString('''
+    if (isMacro) {
+      builder.declareInClass(new DeclarationCode.fromString('''
   hasMacro() => true;
 '''));
+    }
   }
 }
diff --git a/pkg/front_end/test/macro_application/data/tests/to_string.dart.expect b/pkg/front_end/test/macro_application/data/tests/to_string.dart.expect
index 3a56029204f..68d6ea1c939 100644
--- a/pkg/front_end/test/macro_application/data/tests/to_string.dart.expect
+++ b/pkg/front_end/test/macro_application/data/tests/to_string.dart.expect
@@ -12,7 +12,7 @@ class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
-  method /* from org-dartlang-augmentation:/a/b/c/main.dart-0 */ toString() → dynamic {
+  method /* from org-dartlang-augmentation:/a/b/c/main.dart-0 */ toString() → core::String {
     return "A(a=${this.{self::A::a}{dynamic}},b=${this.{self::A::b}{dynamic}})";
   }
 }
@@ -24,7 +24,7 @@ class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
-  method /* from org-dartlang-augmentation:/a/b/c/main.dart-1 */ toString() → dynamic {
+  method /* from org-dartlang-augmentation:/a/b/c/main.dart-1 */ toString() → core::String {
     return "B(c=${this.{self::B::c}{dynamic}},d=${this.{self::B::d}{dynamic}},e=${this.{self::B::e}{dynamic}})";
   }
 }
diff --git a/pkg/front_end/test/spell_checking_list_messages.txt b/pkg/front_end/test/spell_checking_list_messages.txt
index e6964cdc50e..664608e47db 100644
--- a/pkg/front_end/test/spell_checking_list_messages.txt
+++ b/pkg/front_end/test/spell_checking_list_messages.txt
@@ -16,6 +16,9 @@ adjusting
 api
 argument(s)
 assigning
+augment
+augmentation
+augmented
 b
 c
 compilercontext.runincontext
diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index 7313d713260..0a0575a7090 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -41,6 +41,7 @@ asserter
 assure
 asterisk
 atomic
+augmented
 auth
 authority
 autobianchi
diff --git a/pkg/front_end/testcases/macros/class_members.dart b/pkg/front_end/testcases/macros/class_members.dart
new file mode 100644
index 00000000000..12aa81825ee
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart
@@ -0,0 +1,37 @@
+// Copyright (c) 2022, 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 augment 'class_members_lib.dart';
+
+class Class {
+  void existingMethod() {
+    print('existingMethod-origin');
+  }
+
+  external void augmentedMethod();
+
+  void set existingSetter(_) {
+    print('existingSetter-origin');
+  }
+
+  external void set augmentedSetter(_);
+}
+
+test(Class c) {
+  c.orphanedMethod();
+  c.orphanedSetter = 0;
+}
+
+main() {
+  Class c = new Class();
+  c.augmentedMethod();
+  c.injectedMethod();
+  c.existingMethod();
+
+  c.augmentedSetter = 0;
+  c.injectedSetter = 0;
+  c.existingSetter = 0;
+
+  injectedMethod(c);
+}
\ No newline at end of file
diff --git a/pkg/front_end/testcases/macros/class_members.dart.strong.expect b/pkg/front_end/testcases/macros/class_members.dart.strong.expect
new file mode 100644
index 00000000000..52ceebad4e5
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.strong.expect
@@ -0,0 +1,111 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+//   c.orphanedMethod();
+//     ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+//   c.orphanedSetter = 0;
+//     ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    : super core::Object::•()
+    ;
+  method existingMethod() → void {
+    core::print("existingMethod-origin");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedMethod() → void {
+    core::print("augmentedMethod");
+  }
+  set existingSetter(dynamic _) → void {
+    core::print("existingSetter-origin");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedSetter(dynamic _) → void {
+    core::print("augmentedSetter");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void {
+    core::print("injectedMethod");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void {
+    core::print("orphanedMethod");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void {
+    core::print("injectedSetter");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void {
+    core::print("orphanedSetter");
+  }
+}
+static method test(self::Class c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+  c.orphanedMethod();
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedMethod();
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+  c.orphanedSetter = 0;
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedSetter = 0;
+}
+static method main() → dynamic {
+  self::Class c = new self::Class::•();
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+  self::injectedMethod(c);
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void {
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedSetter} = 0;
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void {
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+}
diff --git a/pkg/front_end/testcases/macros/class_members.dart.strong.transformed.expect b/pkg/front_end/testcases/macros/class_members.dart.strong.transformed.expect
new file mode 100644
index 00000000000..52ceebad4e5
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.strong.transformed.expect
@@ -0,0 +1,111 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+//   c.orphanedMethod();
+//     ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+//   c.orphanedSetter = 0;
+//     ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    : super core::Object::•()
+    ;
+  method existingMethod() → void {
+    core::print("existingMethod-origin");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedMethod() → void {
+    core::print("augmentedMethod");
+  }
+  set existingSetter(dynamic _) → void {
+    core::print("existingSetter-origin");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedSetter(dynamic _) → void {
+    core::print("augmentedSetter");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void {
+    core::print("injectedMethod");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void {
+    core::print("orphanedMethod");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void {
+    core::print("injectedSetter");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void {
+    core::print("orphanedSetter");
+  }
+}
+static method test(self::Class c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+  c.orphanedMethod();
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedMethod();
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+  c.orphanedSetter = 0;
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedSetter = 0;
+}
+static method main() → dynamic {
+  self::Class c = new self::Class::•();
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+  self::injectedMethod(c);
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void {
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedSetter} = 0;
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void {
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+}
diff --git a/pkg/front_end/testcases/macros/class_members.dart.textual_outline.expect b/pkg/front_end/testcases/macros/class_members.dart.textual_outline.expect
new file mode 100644
index 00000000000..c5c8d442f39
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.textual_outline.expect
@@ -0,0 +1,9 @@
+import augment 'class_members_lib.dart';
+class Class {
+  void existingMethod() {}
+  external void augmentedMethod();
+  void set existingSetter(_) {}
+  external void set augmentedSetter(_);
+}
+test(Class c) {}
+main() {}
diff --git a/pkg/front_end/testcases/macros/class_members.dart.weak.expect b/pkg/front_end/testcases/macros/class_members.dart.weak.expect
new file mode 100644
index 00000000000..52ceebad4e5
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.weak.expect
@@ -0,0 +1,111 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+//   c.orphanedMethod();
+//     ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+//   c.orphanedSetter = 0;
+//     ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    : super core::Object::•()
+    ;
+  method existingMethod() → void {
+    core::print("existingMethod-origin");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedMethod() → void {
+    core::print("augmentedMethod");
+  }
+  set existingSetter(dynamic _) → void {
+    core::print("existingSetter-origin");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedSetter(dynamic _) → void {
+    core::print("augmentedSetter");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void {
+    core::print("injectedMethod");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void {
+    core::print("orphanedMethod");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void {
+    core::print("injectedSetter");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void {
+    core::print("orphanedSetter");
+  }
+}
+static method test(self::Class c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+  c.orphanedMethod();
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedMethod();
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+  c.orphanedSetter = 0;
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedSetter = 0;
+}
+static method main() → dynamic {
+  self::Class c = new self::Class::•();
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+  self::injectedMethod(c);
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void {
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedSetter} = 0;
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void {
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+}
diff --git a/pkg/front_end/testcases/macros/class_members.dart.weak.modular.expect b/pkg/front_end/testcases/macros/class_members.dart.weak.modular.expect
new file mode 100644
index 00000000000..52ceebad4e5
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.weak.modular.expect
@@ -0,0 +1,111 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+//   c.orphanedMethod();
+//     ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+//   c.orphanedSetter = 0;
+//     ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    : super core::Object::•()
+    ;
+  method existingMethod() → void {
+    core::print("existingMethod-origin");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedMethod() → void {
+    core::print("augmentedMethod");
+  }
+  set existingSetter(dynamic _) → void {
+    core::print("existingSetter-origin");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedSetter(dynamic _) → void {
+    core::print("augmentedSetter");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void {
+    core::print("injectedMethod");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void {
+    core::print("orphanedMethod");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void {
+    core::print("injectedSetter");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void {
+    core::print("orphanedSetter");
+  }
+}
+static method test(self::Class c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+  c.orphanedMethod();
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedMethod();
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+  c.orphanedSetter = 0;
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedSetter = 0;
+}
+static method main() → dynamic {
+  self::Class c = new self::Class::•();
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+  self::injectedMethod(c);
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void {
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedSetter} = 0;
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void {
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+}
diff --git a/pkg/front_end/testcases/macros/class_members.dart.weak.outline.expect b/pkg/front_end/testcases/macros/class_members.dart.weak.outline.expect
new file mode 100644
index 00000000000..49e7b5107c3
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.weak.outline.expect
@@ -0,0 +1,61 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    ;
+  method existingMethod() → void
+    ;
+  external method augmentedMethod() → void;
+  set existingSetter(dynamic _) → void
+    ;
+  external set augmentedSetter(dynamic _) → void;
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void
+    ;
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void
+    ;
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void
+    ;
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void
+    ;
+}
+static method test(self::Class c) → dynamic
+  ;
+static method main() → dynamic
+  ;
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void
+  ;
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void
+  ;
diff --git a/pkg/front_end/testcases/macros/class_members.dart.weak.transformed.expect b/pkg/front_end/testcases/macros/class_members.dart.weak.transformed.expect
new file mode 100644
index 00000000000..52ceebad4e5
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members.dart.weak.transformed.expect
@@ -0,0 +1,111 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:9:8: Error: Member 'existingMethod' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:8:8: Context: This is the existing member.
+//   void existingMethod() {
+//        ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:15:16: Error: Augmentation member 'orphanedMethod' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void orphanedMethod() {
+//                ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:21:12: Error: Member 'existingSetter' conflicts with an existing member of the same name in the augmented class.
+// Try changing the name to an existing member or adding an 'augment' modifier.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+// pkg/front_end/testcases/macros/class_members.dart:14:12: Context: This is the existing member.
+//   void set existingSetter(_) {
+//            ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members_lib.dart:27:20: Error: Augmentation member 'orphanedSetter' doesn't match a member in the augmented class.
+// Try changing the name to an existing member or removing the 'augment' modifier.
+//   augment void set orphanedSetter(_) {
+//                    ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+//   c.orphanedMethod();
+//     ^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+//  - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+// Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+//   c.orphanedSetter = 0;
+//     ^^^^^^^^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///class_members.dart";
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class
+    : super core::Object::•()
+    ;
+  method existingMethod() → void {
+    core::print("existingMethod-origin");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedMethod() → void {
+    core::print("augmentedMethod");
+  }
+  set existingSetter(dynamic _) → void {
+    core::print("existingSetter-origin");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ augmentedSetter(dynamic _) → void {
+    core::print("augmentedSetter");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod() → void {
+    core::print("injectedMethod");
+  }
+  method /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedMethod() → void {
+    core::print("orphanedMethod");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ injectedSetter(dynamic _) → void {
+    core::print("injectedSetter");
+  }
+  set /* from org-dartlang-testcase:///class_members_lib.dart */ orphanedSetter(dynamic _) → void {
+    core::print("orphanedSetter");
+  }
+}
+static method test(self::Class c) → dynamic {
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:22:5: Error: The method 'orphanedMethod' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing method, or defining a method named 'orphanedMethod'.
+  c.orphanedMethod();
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedMethod();
+  invalid-expression "pkg/front_end/testcases/macros/class_members.dart:23:5: Error: The setter 'orphanedSetter' isn't defined for the class 'Class'.
+ - 'Class' is from 'pkg/front_end/testcases/macros/class_members.dart'.
+Try correcting the name to the name of an existing setter, or defining a setter or field named 'orphanedSetter'.
+  c.orphanedSetter = 0;
+    ^^^^^^^^^^^^^^" in c{<unresolved>}.orphanedSetter = 0;
+}
+static method main() → dynamic {
+  self::Class c = new self::Class::•();
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+  self::injectedMethod(c);
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ augmentTest(self::Class c) → void {
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedMethod}(){() → void};
+  c.{self::Class::orphanedSetter} = 0;
+}
+static method /* from org-dartlang-testcase:///class_members_lib.dart */ injectedMethod(self::Class c) → void {
+  c.{self::Class::augmentedMethod}(){() → void};
+  c.{self::Class::injectedMethod}(){() → void};
+  c.{self::Class::existingMethod}(){() → void};
+  c.{self::Class::augmentedSetter} = 0;
+  c.{self::Class::injectedSetter} = 0;
+  c.{self::Class::existingSetter} = 0;
+}
diff --git a/pkg/front_end/testcases/macros/class_members_lib.dart b/pkg/front_end/testcases/macros/class_members_lib.dart
new file mode 100644
index 00000000000..a5952d546cf
--- /dev/null
+++ b/pkg/front_end/testcases/macros/class_members_lib.dart
@@ -0,0 +1,46 @@
+// Copyright (c) 2022, 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.
+
+augment class Class {
+  augment void augmentedMethod() {
+    print('augmentedMethod');
+  }
+  void existingMethod() {
+    print('existingMethod-duplicate');
+  }
+  void injectedMethod() {
+    print('injectedMethod');
+  }
+  augment void orphanedMethod() {
+    print('orphanedMethod');
+  }
+  augment void set augmentedSetter(_) {
+    print('augmentedSetter');
+  }
+  void set existingSetter(_) {
+    print('existingSetter-duplicate');
+  }
+  void set injectedSetter(_) {
+    print('injectedSetter');
+  }
+  augment void set orphanedSetter(_) {
+    print('orphanedSetter');
+  }
+}
+
+void augmentTest(Class c) {
+  c.orphanedMethod();
+  c.orphanedMethod();
+  c.orphanedSetter = 0;
+}
+
+void injectedMethod(Class c) {
+  c.augmentedMethod();
+  c.injectedMethod();
+  c.existingMethod();
+
+  c.augmentedSetter = 0;
+  c.injectedSetter = 0;
+  c.existingSetter = 0;
+}
\ No newline at end of file
diff --git a/pkg/front_end/testcases/textual_outline.status b/pkg/front_end/testcases/textual_outline.status
index afa3f8adf00..fbb0de5154d 100644
--- a/pkg/front_end/testcases/textual_outline.status
+++ b/pkg/front_end/testcases/textual_outline.status
@@ -162,6 +162,7 @@ late_lowering/override_getter_setter: FormatterCrash
 late_lowering/skip_late_final_uninitialized_instance_fields/main: FormatterCrash
 late_lowering/uninitialized_non_nullable_late_fields: FormatterCrash
 macros/augment_class: FormatterCrash
+macros/class_members: FormatterCrash
 macros/macro_class: FormatterCrash
 nnbd/abstract_field_errors: FormatterCrash
 nnbd/covariant_late_field: FormatterCrash
diff --git a/pkg/front_end/tool/dart_doctest_impl.dart b/pkg/front_end/tool/dart_doctest_impl.dart
index 5706ec99ad7..544345dc486 100644
--- a/pkg/front_end/tool/dart_doctest_impl.dart
+++ b/pkg/front_end/tool/dart_doctest_impl.dart
@@ -918,7 +918,8 @@ class DocTestSourceLoader extends SourceLoader {
       required LanguageVersion packageLanguageVersion,
       SourceLibraryBuilder? origin,
       kernel.Library? referencesFrom,
-      bool? referenceIsPartOwner}) {
+      bool? referenceIsPartOwner,
+      bool isAugmentation: false}) {
     if (importUri == DocTestIncrementalCompiler.dartDocTestUri) {
       HybridFileSystem hfs = target.fileSystem as HybridFileSystem;
       MemoryFileSystem fs = hfs.memory;
@@ -935,6 +936,7 @@ class DocTestSourceLoader extends SourceLoader {
         packageLanguageVersion: packageLanguageVersion,
         origin: origin,
         referencesFrom: referencesFrom,
-        referenceIsPartOwner: referenceIsPartOwner);
+        referenceIsPartOwner: referenceIsPartOwner,
+        isAugmentation: isAugmentation);
   }
 }