[cfe] Handle external extension instance fields

Change-Id: Ia6d397e2be3cc46f252b679007f6f7b45096420f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/212569 Reviewed-by: Dmitry Stefantsov <dmitryas@google.com> Commit-Queue: Johnni Winther <johnniwinther@google.com>
2024-10-02 23:59:16 +00:00 · 2021-09-06 15:52:39 +00:00 · 2021-09-06 15:52:39 +00:00 · 8f270ea432
parent 2b41685519
commit 8f270ea432
32 changed files with 804 additions and 338 deletions
--- a/pkg/front_end/lib/src/fasta/builder/builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/builder.dart
@ -36,6 +36,8 @@ abstract class Builder {

  bool get isGetter;

+  bool get isExternal;
+
  /// Returns `true` if this builder is an extension declaration.
  ///
  /// For instance `B` in:
@ -276,6 +278,9 @@ abstract class BuilderImpl implements Builder {
  @override
  bool get isStatic => false;

+  @override
+  bool get isExternal => false;
+
  @override
  bool get isSynthetic => false;

--- a/pkg/front_end/lib/src/fasta/builder/enum_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/enum_builder.dart
@ -55,8 +55,8 @@ import '../modifier.dart'

 import '../scope.dart';

+import '../source/name_scheme.dart';
 import '../source/source_class_builder.dart' show SourceClassBuilder;
-
 import '../source/source_library_builder.dart' show SourceLibraryBuilder;

 import 'builder.dart';
@ -189,7 +189,7 @@ class EnumBuilder extends SourceClassBuilder {
    ///   String toString() => _name;
    /// }

-    FieldNameScheme instanceFieldNameScheme = new FieldNameScheme(
+    NameScheme instanceFieldNameScheme = new NameScheme(
        isInstanceMember: true,
        className: name,
        isExtensionMember: false,
@ -198,7 +198,7 @@ class EnumBuilder extends SourceClassBuilder {
            ? referencesFromIndexed.library.reference
            : parent.library.reference);

-    FieldNameScheme staticFieldNameScheme = new FieldNameScheme(
+    NameScheme staticFieldNameScheme = new NameScheme(
        isInstanceMember: false,
        className: name,
        isExtensionMember: false,
@ -207,8 +207,9 @@ class EnumBuilder extends SourceClassBuilder {
            ? referencesFromIndexed.library.reference
            : parent.library.reference);

-    ProcedureNameScheme procedureNameScheme = new ProcedureNameScheme(
-        isStatic: false,
+    NameScheme procedureNameScheme = new NameScheme(
+        isInstanceMember: true,
+        className: name,
        isExtensionMember: false,
        extensionName: null,
        libraryReference: referencesFromIndexed != null
@ -254,7 +255,6 @@ class EnumBuilder extends SourceClassBuilder {
        charOffset,
        charOffset,
        instanceFieldNameScheme,
-        isInstanceMember: true,
        fieldGetterReference: indexGetterReference,
        fieldSetterReference: indexSetterReference);
    members["index"] = indexBuilder;
@ -268,7 +268,6 @@ class EnumBuilder extends SourceClassBuilder {
        charOffset,
        charOffset,
        instanceFieldNameScheme,
-        isInstanceMember: true,
        fieldGetterReference: _nameGetterReference,
        fieldSetterReference: _nameSetterReference);
    members["_name"] = nameBuilder;
@ -302,7 +301,6 @@ class EnumBuilder extends SourceClassBuilder {
        charOffset,
        charOffset,
        staticFieldNameScheme,
-        isInstanceMember: false,
        fieldGetterReference: valuesGetterReference,
        fieldSetterReference: valuesSetterReference);
    members["values"] = valuesBuilder;
@ -384,7 +382,6 @@ class EnumBuilder extends SourceClassBuilder {
            enumConstantInfo.charOffset,
            enumConstantInfo.charOffset,
            staticFieldNameScheme,
-            isInstanceMember: false,
            fieldGetterReference: getterReference,
            fieldSetterReference: setterReference);
        members[name] = fieldBuilder..next = existing;
--- a/pkg/front_end/lib/src/fasta/builder/extension_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/extension_builder.dart
@ -15,6 +15,7 @@ import '../util/helpers.dart';

 import 'builder.dart';
 import 'declaration_builder.dart';
+import 'field_builder.dart';
 import 'library_builder.dart';
 import 'member_builder.dart';
 import 'metadata_builder.dart';
@ -181,9 +182,21 @@ abstract class ExtensionBuilderImpl extends DeclarationBuilderImpl
      {bool setter: false, bool required: false}) {
    Builder? builder =
        lookupLocalMember(name.text, setter: setter, required: required);
+    if (builder == null && setter) {
+      // When looking up setters, we include assignable fields.
+      builder = lookupLocalMember(name.text, setter: false, required: required);
+      if (builder is! FieldBuilder || !builder.isAssignable) {
+        builder = null;
+      }
+    }
    if (builder != null) {
      if (name.isPrivate && library.library != name.library) {
        builder = null;
+      } else if (builder is FieldBuilder &&
+          !builder.isStatic &&
+          !builder.isExternal) {
+        // Non-external extension instance fields are invalid.
+        builder = null;
      } else if (builder.isDuplicate) {
        // Duplicates are not visible in the instance scope.
        builder = null;
--- a/pkg/front_end/lib/src/fasta/builder/factory_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/factory_builder.dart
@ -23,6 +23,7 @@ import '../messages.dart'

 import '../problems.dart' show unexpected, unhandled;

+import '../source/name_scheme.dart';
 import '../source/source_library_builder.dart' show SourceLibraryBuilder;

 import '../type_inference/type_inferrer.dart';
@ -36,7 +37,6 @@ import 'formal_parameter_builder.dart';
 import 'function_builder.dart';
 import 'member_builder.dart';
 import 'metadata_builder.dart';
-import 'procedure_builder.dart';
 import 'type_builder.dart';
 import 'type_variable_builder.dart';

@ -67,10 +67,10 @@ class SourceFactoryBuilder extends FunctionBuilderImpl {
      int charEndOffset,
      Reference? procedureReference,
      AsyncMarker asyncModifier,
-      ProcedureNameScheme procedureNameScheme,
+      NameScheme nameScheme,
      {String? nativeMethodName})
      : _procedureInternal = new Procedure(
-            procedureNameScheme.getName(ProcedureKind.Factory, name),
+            nameScheme.getProcedureName(ProcedureKind.Factory, name),
            ProcedureKind.Factory,
            new FunctionNode(null),
            fileUri: libraryBuilder.fileUri,
@ -273,7 +273,7 @@ class RedirectingFactoryBuilder extends SourceFactoryBuilder {
      int charOpenParenOffset,
      int charEndOffset,
      Reference? procedureReference,
-      ProcedureNameScheme procedureNameScheme,
+      NameScheme nameScheme,
      String? nativeMethodName,
      this.redirectionTarget)
      : super(
@ -290,7 +290,7 @@ class RedirectingFactoryBuilder extends SourceFactoryBuilder {
            charEndOffset,
            procedureReference,
            AsyncMarker.Sync,
-            procedureNameScheme,
+            nameScheme,
            nativeMethodName: nativeMethodName);

  @override
--- a/pkg/front_end/lib/src/fasta/builder/field_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/field_builder.dart
@ -9,6 +9,7 @@ import 'package:_fe_analyzer_shared/src/scanner/scanner.dart' show Token;
 import 'package:kernel/ast.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/src/legacy_erasure.dart';
+import 'package:kernel/type_algebra.dart';

 import '../constant_context.dart' show ConstantContext;

@ -27,8 +28,9 @@ import '../problems.dart' show internalProblem;

 import '../scope.dart' show Scope;

+import '../source/name_scheme.dart';
+import '../source/source_extension_builder.dart';
 import '../source/source_library_builder.dart' show SourceLibraryBuilder;
-
 import '../source/source_loader.dart' show SourceLoader;

 import '../type_inference/type_inference_engine.dart'
@ -117,9 +119,8 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
      SourceLibraryBuilder libraryBuilder,
      int charOffset,
      int charEndOffset,
-      FieldNameScheme fieldNameScheme,
-      {required bool isInstanceMember,
-      Reference? fieldGetterReference,
+      NameScheme fieldNameScheme,
+      {Reference? fieldGetterReference,
      Reference? fieldSetterReference,
      Reference? lateIsSetGetterReference,
      Reference? lateIsSetSetterReference,
@ -128,8 +129,7 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
      Token? constInitializerToken})
      : _constInitializerToken = constInitializerToken,
        super(libraryBuilder, charOffset) {
-    // ignore: unnecessary_null_comparison
-    assert(isInstanceMember != null);
+    bool isInstanceMember = fieldNameScheme.isInstanceMember;

    Uri fileUri = libraryBuilder.fileUri;
    // If in mixed mode, late lowerings cannot use `null` as a sentinel on
@ -143,6 +143,7 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
      assert(lateGetterReference == null);
      assert(lateSetterReference == null);
      _fieldEncoding = new AbstractOrExternalFieldEncoding(
+          this,
          name,
          fieldNameScheme,
          fileUri,
@ -393,7 +394,7 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
      // notInstanceContext is set to true for extension fields as they
      // ultimately become static.
      fieldType = type!.build(libraryBuilder,
-          nonInstanceContext: isStatic || isExtensionMember);
+          nonInstanceContext: isStatic || (isExtensionMember && !isExternal));
    }
    _fieldEncoding.build(libraryBuilder, this);
  }
@ -520,86 +521,6 @@ class SourceFieldBuilder extends MemberBuilderImpl implements FieldBuilder {
  @override
  List<ClassMember> get localSetters =>
      _localSetters ??= _fieldEncoding.getLocalSetters(this);
-
-  static String createFieldName(FieldNameType type, String name,
-      {required bool isInstanceMember,
-      required String? className,
-      bool isExtensionMethod: false,
-      String? extensionName,
-      bool isSynthesized: false}) {
-    assert(isSynthesized || type == FieldNameType.Field,
-        "Unexpected field name type for non-synthesized field: $type");
-    // ignore: unnecessary_null_comparison
-    assert(isExtensionMethod || isInstanceMember != null,
-        "`isInstanceMember` is null for class member.");
-    assert(!(isExtensionMethod && extensionName == null),
-        "No extension name provided for extension member.");
-    // ignore: unnecessary_null_comparison
-    assert(isInstanceMember == null || !(isInstanceMember && className == null),
-        "No class name provided for instance member.");
-    String baseName;
-    if (!isExtensionMethod) {
-      baseName = name;
-    } else {
-      baseName = "${extensionName}|${name}";
-    }
-
-    if (!isSynthesized) {
-      return baseName;
-    } else {
-      String namePrefix = late_lowering.lateFieldPrefix;
-      if (isInstanceMember) {
-        namePrefix = '$namePrefix${className}#';
-      }
-      switch (type) {
-        case FieldNameType.Field:
-          return "$namePrefix$baseName";
-        case FieldNameType.Getter:
-          return baseName;
-        case FieldNameType.Setter:
-          return baseName;
-        case FieldNameType.IsSetField:
-          return "$namePrefix$baseName${late_lowering.lateIsSetSuffix}";
-      }
-    }
-  }
-}
-
-enum FieldNameType { Field, Getter, Setter, IsSetField }
-
-class FieldNameScheme {
-  final bool isInstanceMember;
-  final String? className;
-  final bool isExtensionMember;
-  final String? extensionName;
-  final Reference? libraryReference;
-
-  FieldNameScheme(
-      {required this.isInstanceMember,
-      required this.className,
-      required this.isExtensionMember,
-      required this.extensionName,
-      required this.libraryReference})
-      // ignore: unnecessary_null_comparison
-      : assert(isInstanceMember != null),
-        // ignore: unnecessary_null_comparison
-        assert(isExtensionMember != null),
-        // ignore: unnecessary_null_comparison
-        assert(!isExtensionMember || extensionName != null),
-        // ignore: unnecessary_null_comparison
-        assert(libraryReference != null);
-
-  Name getName(FieldNameType type, String name, {required bool isSynthesized}) {
-    // ignore: unnecessary_null_comparison
-    assert(isSynthesized != null);
-    String text = SourceFieldBuilder.createFieldName(type, name,
-        isInstanceMember: isInstanceMember,
-        className: className,
-        isExtensionMethod: isExtensionMember,
-        extensionName: extensionName,
-        isSynthesized: isSynthesized);
-    return new Name.byReference(text, libraryReference);
-  }
 }

 /// Strategy pattern for creating different encodings of a declared field.
@ -671,8 +592,8 @@ abstract class FieldEncoding {
 class RegularFieldEncoding implements FieldEncoding {
  late final Field _field;

-  RegularFieldEncoding(String name, FieldNameScheme fieldNameScheme,
-      Uri fileUri, int charOffset, int charEndOffset,
+  RegularFieldEncoding(String name, NameScheme nameScheme, Uri fileUri,
+      int charOffset, int charEndOffset,
      {required bool isFinal,
      required bool isConst,
      required bool isLate,
@ -692,7 +613,7 @@ class RegularFieldEncoding implements FieldEncoding {
        isLate ? (isFinal && hasInitializer) : (isFinal || isConst);
    _field = isImmutable
        ? new Field.immutable(
-            fieldNameScheme.getName(FieldNameType.Field, name,
+            nameScheme.getFieldName(FieldNameType.Field, name,
                isSynthesized: false),
            isFinal: isFinal,
            isConst: isConst,
@ -700,7 +621,7 @@ class RegularFieldEncoding implements FieldEncoding {
            fileUri: fileUri,
            getterReference: getterReference)
        : new Field.mutable(
-            fieldNameScheme.getName(FieldNameType.Field, name,
+            nameScheme.getFieldName(FieldNameType.Field, name,
                isSynthesized: false),
            isFinal: isFinal,
            isLate: isLate,
@ -883,7 +804,7 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {

  AbstractLateFieldEncoding(
      this.name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -901,7 +822,7 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
        _forceIncludeIsSetField =
            isSetStrategy == late_lowering.IsSetStrategy.forceUseIsSetField {
    _field = new Field.mutable(
-        fieldNameScheme.getName(FieldNameType.Field, name, isSynthesized: true),
+        nameScheme.getFieldName(FieldNameType.Field, name, isSynthesized: true),
        fileUri: fileUri,
        getterReference: fieldGetterReference,
        setterReference: fieldSetterReference)
@ -917,7 +838,7 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
      case late_lowering.IsSetStrategy.forceUseIsSetField:
      case late_lowering.IsSetStrategy.useIsSetFieldOrNull:
        _lateIsSetField = new Field.mutable(
-            fieldNameScheme.getName(FieldNameType.IsSetField, name,
+            nameScheme.getFieldName(FieldNameType.IsSetField, name,
                isSynthesized: true),
            fileUri: fileUri,
            getterReference: lateIsSetGetterReference,
@ -929,7 +850,7 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
        break;
    }
    _lateGetter = new Procedure(
-        fieldNameScheme.getName(FieldNameType.Getter, name,
+        nameScheme.getFieldName(FieldNameType.Getter, name,
            isSynthesized: true),
        ProcedureKind.Getter,
        new FunctionNode(null)
@ -941,7 +862,7 @@ abstract class AbstractLateFieldEncoding implements FieldEncoding {
      ..fileEndOffset = charEndOffset
      ..isNonNullableByDefault = true;
    _lateSetter = _createSetter(
-        fieldNameScheme.getName(FieldNameType.Setter, name,
+        nameScheme.getFieldName(FieldNameType.Setter, name,
            isSynthesized: true),
        fileUri,
        charOffset,
@ -1267,7 +1188,7 @@ class LateFieldWithoutInitializerEncoding extends AbstractLateFieldEncoding
    with NonFinalLate, LateWithoutInitializer {
  LateFieldWithoutInitializerEncoding(
      String name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -1281,7 +1202,7 @@ class LateFieldWithoutInitializerEncoding extends AbstractLateFieldEncoding
      late_lowering.IsSetStrategy isSetStrategy)
      : super(
            name,
-            fieldNameScheme,
+            nameScheme,
            fileUri,
            charOffset,
            charEndOffset,
@ -1299,7 +1220,7 @@ class LateFieldWithInitializerEncoding extends AbstractLateFieldEncoding
    with NonFinalLate {
  LateFieldWithInitializerEncoding(
      String name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -1313,7 +1234,7 @@ class LateFieldWithInitializerEncoding extends AbstractLateFieldEncoding
      late_lowering.IsSetStrategy isSetStrategy)
      : super(
            name,
-            fieldNameScheme,
+            nameScheme,
            fileUri,
            charOffset,
            charEndOffset,
@ -1346,7 +1267,7 @@ class LateFinalFieldWithoutInitializerEncoding extends AbstractLateFieldEncoding
    with LateWithoutInitializer {
  LateFinalFieldWithoutInitializerEncoding(
      String name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -1360,7 +1281,7 @@ class LateFinalFieldWithoutInitializerEncoding extends AbstractLateFieldEncoding
      late_lowering.IsSetStrategy isSetStrategy)
      : super(
            name,
-            fieldNameScheme,
+            nameScheme,
            fileUri,
            charOffset,
            charEndOffset,
@ -1394,7 +1315,7 @@ class LateFinalFieldWithoutInitializerEncoding extends AbstractLateFieldEncoding
 class LateFinalFieldWithInitializerEncoding extends AbstractLateFieldEncoding {
  LateFinalFieldWithInitializerEncoding(
      String name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -1408,7 +1329,7 @@ class LateFinalFieldWithInitializerEncoding extends AbstractLateFieldEncoding {
      late_lowering.IsSetStrategy isSetStrategy)
      : super(
            name,
-            fieldNameScheme,
+            nameScheme,
            fileUri,
            charOffset,
            charEndOffset,
@ -1595,15 +1516,19 @@ class _SynthesizedFieldClassMember implements ClassMember {
 }

 class AbstractOrExternalFieldEncoding implements FieldEncoding {
+  final SourceFieldBuilder _fieldBuilder;
  final bool isAbstract;
  final bool isExternal;
+  final bool _isExtensionInstanceMember;

  late Procedure _getter;
  Procedure? _setter;
+  DartType? _type;

  AbstractOrExternalFieldEncoding(
+      this._fieldBuilder,
      String name,
-      FieldNameScheme fieldNameScheme,
+      NameScheme nameScheme,
      Uri fileUri,
      int charOffset,
      int charEndOffset,
@ -1623,45 +1548,138 @@ class AbstractOrExternalFieldEncoding implements FieldEncoding {
        // ignore: unnecessary_null_comparison
        assert(isCovariant != null),
        // ignore: unnecessary_null_comparison
-        assert(isNonNullableByDefault != null) {
-    _getter = new Procedure(
-        fieldNameScheme.getName(FieldNameType.Getter, name,
-            isSynthesized: true),
-        ProcedureKind.Getter,
-        new FunctionNode(null),
-        fileUri: fileUri,
-        reference: getterReference)
-      ..fileOffset = charOffset
-      ..fileEndOffset = charEndOffset
-      ..isNonNullableByDefault = isNonNullableByDefault;
-    if (!isFinal) {
-      VariableDeclaration parameter =
-          new VariableDeclaration("#externalFieldValue")
-            ..isCovariant = isCovariant
-            ..fileOffset = charOffset;
-      _setter = new Procedure(
-          fieldNameScheme.getName(FieldNameType.Setter, name,
-              isSynthesized: true),
-          ProcedureKind.Setter,
-          new FunctionNode(null,
-              positionalParameters: [parameter], returnType: const VoidType())
-            ..fileOffset = charOffset
-            ..fileEndOffset = charEndOffset,
+        assert(isNonNullableByDefault != null),
+        _isExtensionInstanceMember = isExternal &&
+            nameScheme.isExtensionMember &&
+            nameScheme.isInstanceMember {
+    if (_isExtensionInstanceMember) {
+      _getter = new Procedure(
+          nameScheme.getProcedureName(ProcedureKind.Getter, name),
+          ProcedureKind.Method,
+          new FunctionNode(null, positionalParameters: [
+            new VariableDeclaration(extensionThisName)..fileOffset
+          ]),
          fileUri: fileUri,
-          reference: setterReference)
+          reference: getterReference)
        ..fileOffset = charOffset
        ..fileEndOffset = charEndOffset
        ..isNonNullableByDefault = isNonNullableByDefault;
+      if (!isFinal) {
+        VariableDeclaration parameter =
+            new VariableDeclaration("#externalFieldValue")
+              ..isCovariant = isCovariant
+              ..fileOffset = charOffset;
+        _setter = new Procedure(
+            nameScheme.getProcedureName(ProcedureKind.Setter, name),
+            ProcedureKind.Method,
+            new FunctionNode(null,
+                positionalParameters: [
+                  new VariableDeclaration(extensionThisName)..fileOffset,
+                  parameter
+                ],
+                returnType: const VoidType())
+              ..fileOffset = charOffset
+              ..fileEndOffset = charEndOffset,
+            fileUri: fileUri,
+            reference: setterReference)
+          ..fileOffset = charOffset
+          ..fileEndOffset = charEndOffset
+          ..isNonNullableByDefault = isNonNullableByDefault;
+      }
+    } else {
+      _getter = new Procedure(
+          nameScheme.getFieldName(FieldNameType.Getter, name,
+              isSynthesized: true),
+          ProcedureKind.Getter,
+          new FunctionNode(null),
+          fileUri: fileUri,
+          reference: getterReference)
+        ..fileOffset = charOffset
+        ..fileEndOffset = charEndOffset
+        ..isNonNullableByDefault = isNonNullableByDefault;
+      if (!isFinal) {
+        VariableDeclaration parameter =
+            new VariableDeclaration("#externalFieldValue")
+              ..isCovariant = isCovariant
+              ..fileOffset = charOffset;
+        _setter = new Procedure(
+            nameScheme.getFieldName(FieldNameType.Setter, name,
+                isSynthesized: true),
+            ProcedureKind.Setter,
+            new FunctionNode(null,
+                positionalParameters: [parameter], returnType: const VoidType())
+              ..fileOffset = charOffset
+              ..fileEndOffset = charEndOffset,
+            fileUri: fileUri,
+            reference: setterReference)
+          ..fileOffset = charOffset
+          ..fileEndOffset = charEndOffset
+          ..isNonNullableByDefault = isNonNullableByDefault;
+      }
    }
  }

  @override
-  DartType get type => _getter.function.returnType;
+  DartType get type {
+    assert(_type != null,
+        "Type has not been computed for field ${_fieldBuilder.name}.");
+    return _type!;
+  }

  @override
  void set type(DartType value) {
-    _getter.function.returnType = value;
-    _setter?.function.positionalParameters.first.type = value;
+    assert(_type == null || _type is ImplicitFieldType,
+        "Type has already been computed for field ${_fieldBuilder.name}.");
+    _type = value;
+    if (value is! ImplicitFieldType) {
+      if (_isExtensionInstanceMember) {
+        SourceExtensionBuilder extensionBuilder =
+            _fieldBuilder.parent as SourceExtensionBuilder;
+        DartType onType = extensionBuilder.extension.onType;
+        List<TypeParameter> typeParameters =
+            extensionBuilder.extension.typeParameters;
+        if (typeParameters.isNotEmpty) {
+          FreshTypeParameters getterTypeParameters =
+              getFreshTypeParameters(typeParameters);
+          _getter.function.positionalParameters.first.type =
+              getterTypeParameters.substitute(onType);
+          _getter.function.returnType = getterTypeParameters.substitute(value);
+          _getter.function.typeParameters =
+              getterTypeParameters.freshTypeParameters;
+          setParents(
+              getterTypeParameters.freshTypeParameters, _getter.function);
+
+          Procedure? setter = _setter;
+          if (setter != null) {
+            FreshTypeParameters setterTypeParameters =
+                getFreshTypeParameters(typeParameters);
+            setter.function.positionalParameters.first.type =
+                setterTypeParameters.substitute(onType);
+            setter.function.positionalParameters[1].type =
+                setterTypeParameters.substitute(value);
+            setter.function.typeParameters =
+                setterTypeParameters.freshTypeParameters;
+            setParents(
+                setterTypeParameters.freshTypeParameters, setter.function);
+          }
+        } else {
+          _getter.function.returnType = value;
+          _setter?.function.positionalParameters[1].type = value;
+          _getter.function.positionalParameters.first.type = onType;
+          _setter?.function.positionalParameters.first.type = onType;
+        }
+      } else {
+        _getter.function.returnType = value;
+        Procedure? setter = _setter;
+        if (setter != null) {
+          if (setter.kind == ProcedureKind.Method) {
+            setter.function.positionalParameters[1].type = value;
+          } else {
+            setter.function.positionalParameters.first.type = value;
+          }
+        }
+      }
+    }
  }

  @override
--- a/pkg/front_end/lib/src/fasta/builder/member_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/member_builder.dart
@ -68,6 +68,7 @@ abstract class MemberBuilder implements ModifierBuilder {
  // TODO(johnniwinther): Remove this and create a [ProcedureBuilder] interface.
  ProcedureKind? get kind;

+  @override
  bool get isExternal;

  bool get isAbstract;
--- a/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/named_type_builder.dart
@ -276,7 +276,7 @@ class NamedTypeBuilder extends TypeBuilder {
  // TODO(johnniwinther): Store [origin] on the built type.
  DartType buildInternal(LibraryBuilder library,
      {TypedefType? origin,
-      bool? nonInstanceContext,
+      required bool? nonInstanceContext,
      required bool forTypeLiteral}) {
    assert(declaration != null, "Declaration has not been resolved on $this.");
    // TODO(johnniwinther): Change `nonInstanceContext == true` to
--- a/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
@ -10,6 +10,7 @@ import '../kernel/member_covariance.dart';

 import '../loader.dart' show Loader;

+import '../source/name_scheme.dart';
 import '../source/source_library_builder.dart' show SourceLibraryBuilder;

 import 'builder.dart';
@ -94,7 +95,7 @@ class SourceProcedureBuilder extends FunctionBuilderImpl
      Reference? procedureReference,
      this._tearOffReference,
      AsyncMarker asyncModifier,
-      ProcedureNameScheme procedureNameScheme,
+      NameScheme nameScheme,
      {required bool isExtensionMember,
      required bool isInstanceMember,
      String? nativeMethodName})
@ -107,7 +108,7 @@ class SourceProcedureBuilder extends FunctionBuilderImpl
        super(metadata, modifiers, returnType, name, typeVariables, formals,
            libraryBuilder, charOffset, nativeMethodName) {
    _procedure = new Procedure(
-        procedureNameScheme.getName(kind, name),
+        nameScheme.getProcedureName(kind, name),
        isExtensionInstanceMember ? ProcedureKind.Method : kind,
        new FunctionNode(null),
        fileUri: libraryBuilder.fileUri,
@ -119,7 +120,7 @@ class SourceProcedureBuilder extends FunctionBuilderImpl
    this.asyncModifier = asyncModifier;
    if (isExtensionMember && isInstanceMember && kind == ProcedureKind.Method) {
      _extensionTearOff ??= new Procedure(
-          procedureNameScheme.getName(ProcedureKind.Getter, name),
+          nameScheme.getProcedureName(ProcedureKind.Getter, name),
          ProcedureKind.Method,
          new FunctionNode(null),
          isStatic: true,
@ -310,35 +311,6 @@ class SourceProcedureBuilder extends FunctionBuilderImpl
    return _procedure;
  }

-  static String createProcedureName(bool isExtensionMethod, bool isStatic,
-      ProcedureKind kind, String? extensionName, String name) {
-    if (isExtensionMethod) {
-      String kindInfix = '';
-      if (!isStatic) {
-        // Instance getter and setter are converted to methods so we use an
-        // infix to make their names unique.
-        switch (kind) {
-          case ProcedureKind.Getter:
-            kindInfix = 'get#';
-            break;
-          case ProcedureKind.Setter:
-            kindInfix = 'set#';
-            break;
-          case ProcedureKind.Method:
-          case ProcedureKind.Operator:
-            kindInfix = '';
-            break;
-          case ProcedureKind.Factory:
-            throw new UnsupportedError(
-                'Unexpected extension method kind ${kind}');
-        }
-      }
-      return '${extensionName}|${kindInfix}${name}';
-    } else {
-      return name;
-    }
-  }
-
  /// Creates a top level function that creates a tear off of an extension
  /// instance method.
  ///
@ -591,33 +563,3 @@ class SourceProcedureMember extends BuilderClassMember {
        memberBuilder == other.memberBuilder;
  }
 }
-
-class ProcedureNameScheme {
-  final bool isExtensionMember;
-  final bool isStatic;
-  final String? extensionName;
-  final Reference libraryReference;
-
-  ProcedureNameScheme(
-      {required this.isExtensionMember,
-      required this.isStatic,
-      this.extensionName,
-      required this.libraryReference})
-      // ignore: unnecessary_null_comparison
-      : assert(isExtensionMember != null),
-        // ignore: unnecessary_null_comparison
-        assert(isStatic != null),
-        // ignore: unnecessary_null_comparison
-        assert(!isExtensionMember || extensionName != null),
-        // ignore: unnecessary_null_comparison
-        assert(libraryReference != null);
-
-  Name getName(ProcedureKind kind, String name) {
-    // ignore: unnecessary_null_comparison
-    assert(kind != null);
-    return new Name.byReference(
-        SourceProcedureBuilder.createProcedureName(
-            isExtensionMember, isStatic, kind, extensionName, name),
-        libraryReference);
-  }
-}
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@ -6845,7 +6845,8 @@ class BodyBuilder extends ScopeListener<JumpTarget>
          builder.declaration as TypeVariableBuilder;
      TypeParameter typeParameter = typeParameterBuilder.parameter;
      LocatedMessage message;
-      bool extensionField = member.isExtensionMember && member.isField;
+      bool extensionField =
+          member.isExtensionMember && member.isField && !member.isExternal;
      if ((extensionField || !isDeclarationInstanceContext) &&
          (typeParameter.parent is Class ||
              typeParameter.parent is Extension)) {
--- a/pkg/front_end/lib/src/fasta/kernel/expression_generator.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/expression_generator.dart
@ -1942,6 +1942,10 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
        assert(!getterBuilder.isStatic);
        MemberBuilder memberBuilder = getterBuilder as MemberBuilder;
        invokeTarget = memberBuilder.invokeTarget as Procedure?;
+      } else if (getterBuilder.isField) {
+        assert(!getterBuilder.isStatic);
+        MemberBuilder memberBuilder = getterBuilder as MemberBuilder;
+        readTarget = memberBuilder.invokeTarget as Procedure?;
      } else {
        return unhandled(
            "$getterBuilder (${getterBuilder.runtimeType})",
@ -1959,6 +1963,10 @@ class ExplicitExtensionInstanceAccessGenerator extends Generator {
        assert(!setterBuilder.isStatic);
        MemberBuilder memberBuilder = setterBuilder as MemberBuilder;
        writeTarget = memberBuilder.writeTarget as Procedure?;
+      } else if (setterBuilder.isField) {
+        assert(!setterBuilder.isStatic);
+        MemberBuilder memberBuilder = setterBuilder as MemberBuilder;
+        writeTarget = memberBuilder.writeTarget as Procedure?;
      } else {
        return unhandled(
            "$setterBuilder (${setterBuilder.runtimeType})",
@ -2598,7 +2606,7 @@ class ExplicitExtensionAccessGenerator extends Generator {
  Generator _createInstanceAccess(Token token, Name name,
      {bool isNullAware: false}) {
    Builder? getter = extensionBuilder.lookupLocalMemberByName(name);
-    if (getter != null && (getter.isStatic || getter.isField)) {
+    if (getter != null && getter.isStatic) {
      getter = null;
    }
    Builder? setter =
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@ -67,6 +67,7 @@ import '../messages.dart'
        templateSuperclassHasNoDefaultConstructor;
 import '../problems.dart' show unhandled;
 import '../scope.dart' show AmbiguousBuilder;
+import '../source/name_scheme.dart';
 import '../source/source_class_builder.dart' show SourceClassBuilder;
 import '../source/source_library_builder.dart'
    show LanguageVersion, SourceLibraryBuilder;
@ -1185,7 +1186,7 @@ class KernelTarget extends TargetImplementation {
    assert(() {
      Set<String> patchFieldNames = {};
      builder.forEachDeclaredField((String name, FieldBuilder fieldBuilder) {
-        patchFieldNames.add(SourceFieldBuilder.createFieldName(
+        patchFieldNames.add(NameScheme.createFieldName(
          FieldNameType.Field,
          name,
          isInstanceMember: fieldBuilder.isClassInstanceMember,
--- a/pkg/front_end/lib/src/fasta/source/name_scheme.dart
+++ b/pkg/front_end/lib/src/fasta/source/name_scheme.dart
@ -0,0 +1,137 @@
+// Copyright (c) 2021, 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 'package:kernel/ast.dart';
+
+import '../kernel/late_lowering.dart' as late_lowering;
+
+enum FieldNameType { Field, Getter, Setter, IsSetField }
+
+class NameScheme {
+  final bool isInstanceMember;
+  final String? className;
+  final bool isExtensionMember;
+  final String? extensionName;
+  final Reference? libraryReference;
+
+  NameScheme(
+      {required this.isInstanceMember,
+      required this.className,
+      required this.isExtensionMember,
+      required this.extensionName,
+      required this.libraryReference})
+      // ignore: unnecessary_null_comparison
+      : assert(isInstanceMember != null),
+        // ignore: unnecessary_null_comparison
+        assert(isExtensionMember != null),
+        // ignore: unnecessary_null_comparison
+        assert(!isExtensionMember || extensionName != null),
+        // ignore: unnecessary_null_comparison
+        assert(libraryReference != null);
+
+  bool get isStatic => !isInstanceMember;
+
+  Name getFieldName(FieldNameType type, String name,
+      {required bool isSynthesized}) {
+    // ignore: unnecessary_null_comparison
+    assert(isSynthesized != null);
+    String text = createFieldName(type, name,
+        isInstanceMember: isInstanceMember,
+        className: className,
+        isExtensionMethod: isExtensionMember,
+        extensionName: extensionName,
+        isSynthesized: isSynthesized);
+    return new Name.byReference(text, libraryReference);
+  }
+
+  static String createFieldName(FieldNameType type, String name,
+      {required bool isInstanceMember,
+      required String? className,
+      bool isExtensionMethod: false,
+      String? extensionName,
+      bool isSynthesized: false}) {
+    assert(isSynthesized || type == FieldNameType.Field,
+        "Unexpected field name type for non-synthesized field: $type");
+    // ignore: unnecessary_null_comparison
+    assert(isExtensionMethod || isInstanceMember != null,
+        "`isInstanceMember` is null for class member.");
+    assert(!(isExtensionMethod && extensionName == null),
+        "No extension name provided for extension member.");
+    // ignore: unnecessary_null_comparison
+    assert(isInstanceMember == null || !(isInstanceMember && className == null),
+        "No class name provided for instance member.");
+    String baseName;
+    if (!isExtensionMethod) {
+      baseName = name;
+    } else {
+      baseName = "${extensionName}|${name}";
+    }
+
+    if (!isSynthesized) {
+      return baseName;
+    } else {
+      String namePrefix = late_lowering.lateFieldPrefix;
+      if (isInstanceMember) {
+        namePrefix = '$namePrefix${className}#';
+      }
+      switch (type) {
+        case FieldNameType.Field:
+          return "$namePrefix$baseName";
+        case FieldNameType.Getter:
+          return baseName;
+        case FieldNameType.Setter:
+          return baseName;
+        case FieldNameType.IsSetField:
+          return "$namePrefix$baseName${late_lowering.lateIsSetSuffix}";
+      }
+    }
+  }
+
+  Name getProcedureName(ProcedureKind kind, String name) {
+    // ignore: unnecessary_null_comparison
+    assert(kind != null);
+    return new Name.byReference(
+        createProcedureName(
+            isExtensionMethod: isExtensionMember,
+            isStatic: isStatic,
+            kind: kind,
+            extensionName: extensionName,
+            name: name),
+        libraryReference);
+  }
+
+  static String createProcedureName(
+      {required bool isExtensionMethod,
+      required bool isStatic,
+      required ProcedureKind kind,
+      String? extensionName,
+      required String name}) {
+    if (isExtensionMethod) {
+      assert(extensionName != null);
+      String kindInfix = '';
+      if (!isStatic) {
+        // Instance getter and setter are converted to methods so we use an
+        // infix to make their names unique.
+        switch (kind) {
+          case ProcedureKind.Getter:
+            kindInfix = 'get#';
+            break;
+          case ProcedureKind.Setter:
+            kindInfix = 'set#';
+            break;
+          case ProcedureKind.Method:
+          case ProcedureKind.Operator:
+            kindInfix = '';
+            break;
+          case ProcedureKind.Factory:
+            throw new UnsupportedError(
+                'Unexpected extension method kind ${kind}');
+        }
+      }
+      return '${extensionName}|${kindInfix}${name}';
+    } else {
+      return name;
+    }
+  }
+}
--- a/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart
@ -93,6 +93,8 @@ class SourceExtensionBuilder extends ExtensionBuilderImpl {
  Extension build(
      SourceLibraryBuilder libraryBuilder, LibraryBuilder coreLibrary,
      {required bool addMembersToLibrary}) {
+    _extension.onType = onType.build(libraryBuilder);
+
    SourceLibraryBuilder.checkMemberConflicts(library, scope,
        checkForInstanceVsStaticConflict: true,
        checkForMethodVsSetterConflict: true);
@ -191,8 +193,6 @@ class SourceExtensionBuilder extends ExtensionBuilderImpl {

    scope.forEach(buildBuilders);

-    _extension.onType = onType.build(libraryBuilder);
-
    return _extension;
  }

--- a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
@ -122,12 +122,10 @@ import '../scope.dart';

 import '../type_inference/type_inferrer.dart' show TypeInferrerImpl;

+import 'name_scheme.dart';
 import 'source_class_builder.dart' show SourceClassBuilder;
-
 import 'source_extension_builder.dart' show SourceExtensionBuilder;
-
 import 'source_loader.dart' show SourceLoader;
-
 import 'source_type_alias_builder.dart';

 class SourceLibraryBuilder extends LibraryBuilderImpl {
@ -2227,7 +2225,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
    Reference? lateGetterReference;
    Reference? lateSetterReference;

-    FieldNameScheme fieldNameScheme = new FieldNameScheme(
+    NameScheme nameScheme = new NameScheme(
        isInstanceMember: isInstanceMember,
        className: className,
        isExtensionMember: isExtensionMember,
@ -2236,14 +2234,14 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
    if (referencesFrom != null) {
      IndexedContainer indexedContainer =
          (_currentClassReferencesFromIndexed ?? referencesFromIndexed)!;
-      Name nameToLookupName = fieldNameScheme.getName(FieldNameType.Field, name,
+      Name nameToLookupName = nameScheme.getFieldName(FieldNameType.Field, name,
          isSynthesized: fieldIsLateWithLowering);
      fieldGetterReference =
          indexedContainer.lookupGetterReference(nameToLookupName);
      fieldSetterReference =
          indexedContainer.lookupSetterReference(nameToLookupName);
      if (fieldIsLateWithLowering) {
-        Name lateIsSetNameName = fieldNameScheme.getName(
+        Name lateIsSetNameName = nameScheme.getFieldName(
            FieldNameType.IsSetField, name,
            isSynthesized: fieldIsLateWithLowering);
        lateIsSetGetterReference =
@ -2251,10 +2249,10 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
        lateIsSetSetterReference =
            indexedContainer.lookupSetterReference(lateIsSetNameName);
        lateGetterReference = indexedContainer.lookupGetterReference(
-            fieldNameScheme.getName(FieldNameType.Getter, name,
+            nameScheme.getFieldName(FieldNameType.Getter, name,
                isSynthesized: fieldIsLateWithLowering));
        lateSetterReference = indexedContainer.lookupSetterReference(
-            fieldNameScheme.getName(FieldNameType.Setter, name,
+            nameScheme.getFieldName(FieldNameType.Setter, name,
                isSynthesized: fieldIsLateWithLowering));
      }
    }
@ -2268,8 +2266,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
        this,
        charOffset,
        charEndOffset,
-        fieldNameScheme,
-        isInstanceMember: isInstanceMember,
+        nameScheme,
        fieldGetterReference: fieldGetterReference,
        fieldSetterReference: fieldSetterReference,
        lateIsSetGetterReference: lateIsSetGetterReference,
@ -2371,12 +2368,16 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
    assert(!isExtensionMember ||
        currentTypeParameterScopeBuilder.kind ==
            TypeParameterScopeKind.extensionDeclaration);
+    String? className = (isInstanceMember && !isExtensionMember)
+        ? currentTypeParameterScopeBuilder.name
+        : null;
    String? extensionName =
        isExtensionMember ? currentTypeParameterScopeBuilder.name : null;
-    ProcedureNameScheme procedureNameScheme = new ProcedureNameScheme(
+    NameScheme nameScheme = new NameScheme(
        isExtensionMember: isExtensionMember,
+        className: className,
        extensionName: extensionName,
-        isStatic: !isInstanceMember,
+        isInstanceMember: isInstanceMember,
        libraryReference: referencesFrom?.reference ?? library.reference);

    if (returnType == null) {
@ -2390,7 +2391,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
    Reference? procedureReference;
    Reference? tearOffReference;
    if (referencesFrom != null) {
-      Name nameToLookup = procedureNameScheme.getName(kind, name);
+      Name nameToLookup = nameScheme.getProcedureName(kind, name);
      if (_currentClassReferencesFromIndexed != null) {
        if (kind == ProcedureKind.Setter) {
          procedureReference = _currentClassReferencesFromIndexed!
@ -2411,7 +2412,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
        }
        if (isExtensionMember && kind == ProcedureKind.Method) {
          tearOffReference = referencesFromIndexed!.lookupGetterReference(
-              procedureNameScheme.getName(ProcedureKind.Getter, name));
+              nameScheme.getProcedureName(ProcedureKind.Getter, name));
        }
      }
    }
@ -2431,7 +2432,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
        procedureReference,
        tearOffReference,
        asyncModifier,
-        procedureNameScheme,
+        nameScheme,
        isExtensionMember: isExtensionMember,
        isInstanceMember: isInstanceMember,
        nativeMethodName: nativeMethodName);
@ -2474,10 +2475,11 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
      procedureName = name as String;
    }

-    ProcedureNameScheme procedureNameScheme = new ProcedureNameScheme(
+    NameScheme procedureNameScheme = new NameScheme(
        isExtensionMember: false,
+        className: null,
        extensionName: null,
-        isStatic: true,
+        isInstanceMember: false,
        libraryReference: referencesFrom != null
            ? (_currentClassReferencesFromIndexed ?? referencesFromIndexed)!
                .library
--- a/pkg/front_end/lib/src/fasta/source/source_loader.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_loader.dart
@ -106,8 +106,6 @@ import '../loader.dart' show Loader, untranslatableUriScheme;

 import '../problems.dart' show internalProblem;

-import '../source/stack_listener_impl.dart' show offsetForToken;
-
 import '../type_inference/type_inference_engine.dart';
 import '../type_inference/type_inferrer.dart';

@ -115,10 +113,12 @@ import '../util/helpers.dart';

 import 'diet_listener.dart' show DietListener;
 import 'diet_parser.dart' show DietParser, useImplicitCreationExpressionInCfe;
+import 'name_scheme.dart';
 import 'outline_builder.dart' show OutlineBuilder;
 import 'source_class_builder.dart' show SourceClassBuilder;
 import 'source_library_builder.dart' show SourceLibraryBuilder;
 import 'source_type_alias_builder.dart';
+import 'stack_listener_impl.dart' show offsetForToken;

 class SourceLoader extends Loader {
  /// The [FileSystem] which should be used to access files.
@ -551,9 +551,11 @@ class SourceLoader extends Loader {
        null,
        null,
        AsyncMarker.Sync,
-        new ProcedureNameScheme(
+        new NameScheme(
+            className: null,
+            extensionName: null,
            isExtensionMember: false,
-            isStatic: true,
+            isInstanceMember: false,
            libraryReference: libraryBuilder.library.reference),
        isInstanceMember: false,
        isExtensionMember: false)
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@ -1039,22 +1039,31 @@ class TypeInferrerImpl implements TypeInferrer {

        if (typeSchemaEnvironment.isSubtypeOf(
            receiverType, onType, SubtypeCheckMode.withNullabilities)) {
+          ObjectAccessTarget target = const ObjectAccessTarget.missing();
+          if (thisBuilder != null && !thisBuilder.isStatic) {
+            if (thisBuilder.isField) {
+              if (thisBuilder.isExternal) {
+                target = new ObjectAccessTarget.extensionMember(
+                    setter ? thisBuilder.writeTarget! : thisBuilder.readTarget!,
+                    thisBuilder.readTarget,
+                    setter ? ProcedureKind.Setter : ProcedureKind.Getter,
+                    inferredTypeArguments,
+                    isPotentiallyNullable: isPotentiallyNullableAccess);
+              }
+            } else {
+              target = new ObjectAccessTarget.extensionMember(
+                  setter ? thisBuilder.writeTarget! : thisBuilder.invokeTarget!,
+                  thisBuilder.readTarget,
+                  thisBuilder.kind!,
+                  inferredTypeArguments,
+                  isPotentiallyNullable: isPotentiallyNullableAccess);
+            }
+          }
          ExtensionAccessCandidate candidate = new ExtensionAccessCandidate(
              (thisBuilder ?? otherBuilder)!,
              onType,
              onTypeInstantiateToBounds,
-              thisBuilder != null &&
-                      !thisBuilder.isField &&
-                      !thisBuilder.isStatic
-                  ? new ObjectAccessTarget.extensionMember(
-                      setter
-                          ? thisBuilder.writeTarget!
-                          : thisBuilder.invokeTarget!,
-                      thisBuilder.readTarget,
-                      thisBuilder.kind!,
-                      inferredTypeArguments,
-                      isPotentiallyNullable: isPotentiallyNullableAccess)
-                  : const ObjectAccessTarget.missing(),
+              target,
              isPlatform: extensionBuilder.library.importUri.scheme == 'dart');
          if (noneMoreSpecific.isNotEmpty) {
            bool isMostSpecific = true;
--- a/pkg/front_end/testcases/extensions/external.dart
+++ b/pkg/front_end/testcases/extensions/external.dart
@ -0,0 +1,63 @@
+// Copyright (c) 2021, 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.
+
+extension Extension<T extends num> on List<T> {
+  external T field;
+  external static int staticField;
+  external final T finalField;
+  external static final int staticFinalField;
+  external T method();
+  external static int staticMethod();
+  external T get getter;
+  external static int get staticGetter;
+  external void set setter(T value);
+  external static void set staticSetter(int value);
+  external T get property;
+  external void set property(T value);
+  external static int get staticProperty;
+  external static void set staticProperty(int value);
+  external final T fieldSetter;
+  external void set fieldSetter(T value);
+  external static final int staticFieldSetter;
+  external static void set staticFieldSetter(int value);
+}
+
+test() {
+  List<int> list = [];
+  int value = list.field;
+  list.field = value;
+  value = list.finalField;
+  value = list.method();
+  value = list.getter;
+  list.setter = value;
+  value = list.property;
+  list.property = value;
+  value = list.fieldSetter;
+  list.fieldSetter = value;
+
+  List<int> iterable = list;
+  num n = Extension<num>(iterable).field;
+  Extension<num>(iterable).field = n;
+  n = Extension<num>(iterable).finalField;
+  n = Extension<num>(iterable).method();
+  n = Extension<num>(iterable).getter;
+  Extension<num>(iterable).setter = n;
+  n = Extension<num>(iterable).property;
+  Extension<num>(iterable).property = n;
+  n = Extension<num>(iterable).fieldSetter;
+  Extension<num>(iterable).fieldSetter = n;
+
+  value = Extension.staticField;
+  Extension.staticField = value;
+  value = Extension.staticFinalField;
+  value = Extension.staticMethod();
+  value = Extension.staticGetter;
+  Extension.staticSetter = value;
+  value = Extension.staticProperty;
+  Extension.staticProperty = value;
+  value = Extension.staticFieldSetter;
+  Extension.staticFieldSetter = value;
+}
+
+main() {}
--- a/pkg/front_end/testcases/extensions/external.dart.textual_outline.expect
+++ b/pkg/front_end/testcases/extensions/external.dart.textual_outline.expect
@ -0,0 +1,23 @@
+extension Extension<T extends num> on List<T> {
+  external T field;
+  external static int staticField;
+  external final T finalField;
+  external static final int staticFinalField;
+  external T method();
+  external static int staticMethod();
+  external T get getter;
+  external static int get staticGetter;
+  external void set setter(T value);
+  external static void set staticSetter(int value);
+  external T get property;
+  external void set property(T value);
+  external static int get staticProperty;
+  external static void set staticProperty(int value);
+  external final T fieldSetter;
+  external void set fieldSetter(T value);
+  external static final int staticFieldSetter;
+  external static void set staticFieldSetter(int value);
+}
+
+test() {}
+main() {}
--- a/pkg/front_end/testcases/extensions/external.dart.textual_outline_modelled.expect
+++ b/pkg/front_end/testcases/extensions/external.dart.textual_outline_modelled.expect
@ -0,0 +1,23 @@
+extension Extension<T extends num> on List<T> {
+  external T field;
+  external T get getter;
+  external T get property;
+  external T method();
+  external final T fieldSetter;
+  external final T finalField;
+  external static final int staticFieldSetter;
+  external static final int staticFinalField;
+  external static int get staticGetter;
+  external static int get staticProperty;
+  external static int staticField;
+  external static int staticMethod();
+  external static void set staticFieldSetter(int value);
+  external static void set staticProperty(int value);
+  external static void set staticSetter(int value);
+  external void set fieldSetter(T value);
+  external void set property(T value);
+  external void set setter(T value);
+}
+
+main() {}
+test() {}
--- a/pkg/front_end/testcases/extensions/external.dart.weak.expect
+++ b/pkg/front_end/testcases/extensions/external.dart.weak.expect
@ -0,0 +1,84 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::num> on core::List<T> {
+  get field = self::Extension|get#field;
+  set field = self::Extension|set#field;
+  static get staticField = get self::Extension|staticField;
+  static set staticField = set self::Extension|staticField;
+  get finalField = self::Extension|get#finalField;
+  static get staticFinalField = get self::Extension|staticFinalField;
+  method method = self::Extension|method;
+  tearoff method = self::Extension|get#method;
+  static method staticMethod = self::Extension|staticMethod;
+  get getter = self::Extension|get#getter;
+  static get staticGetter = get self::Extension|staticGetter;
+  get property = self::Extension|get#property;
+  static get staticProperty = get self::Extension|staticProperty;
+  get fieldSetter = self::Extension|get#fieldSetter;
+  static get staticFieldSetter = get self::Extension|staticFieldSetter;
+  set setter = self::Extension|set#setter;
+  static set staticSetter = set self::Extension|staticSetter;
+  set property = self::Extension|set#property;
+  static set staticProperty = set self::Extension|staticProperty;
+  set fieldSetter = self::Extension|set#fieldSetter;
+  static set staticFieldSetter = set self::Extension|staticFieldSetter;
+}
+external static method Extension|get#field<T extends core::num>(core::List<self::Extension|get#field::T> #this) → self::Extension|get#field::T;
+external static method Extension|set#field<T extends core::num>(core::List<self::Extension|set#field::T> #this, self::Extension|set#field::T #externalFieldValue) → void;
+external static get Extension|staticField() → core::int;
+external static set Extension|staticField(core::int #externalFieldValue) → void;
+external static method Extension|get#finalField<T extends core::num>(core::List<self::Extension|get#finalField::T> #this) → self::Extension|get#finalField::T;
+external static get Extension|staticFinalField() → core::int;
+external static method Extension|method<T extends core::num>(lowered final core::List<self::Extension|method::T> #this) → self::Extension|method::T;
+static method Extension|get#method<T extends core::num>(lowered final core::List<self::Extension|get#method::T> #this) → () → self::Extension|get#method::T
+  return () → self::Extension|get#method::T => self::Extension|method<self::Extension|get#method::T>(#this);
+external static method Extension|staticMethod() → core::int;
+external static method Extension|get#getter<T extends core::num>(lowered final core::List<self::Extension|get#getter::T> #this) → self::Extension|get#getter::T;
+external static get Extension|staticGetter() → core::int;
+external static method Extension|set#setter<T extends core::num>(lowered final core::List<self::Extension|set#setter::T> #this, self::Extension|set#setter::T value) → void;
+external static set Extension|staticSetter(core::int value) → void;
+external static method Extension|get#property<T extends core::num>(lowered final core::List<self::Extension|get#property::T> #this) → self::Extension|get#property::T;
+external static method Extension|set#property<T extends core::num>(lowered final core::List<self::Extension|set#property::T> #this, self::Extension|set#property::T value) → void;
+external static get Extension|staticProperty() → core::int;
+external static set Extension|staticProperty(core::int value) → void;
+external static method Extension|get#fieldSetter<T extends core::num>(core::List<self::Extension|get#fieldSetter::T> #this) → self::Extension|get#fieldSetter::T;
+external static method Extension|set#fieldSetter<T extends core::num>(lowered final core::List<self::Extension|set#fieldSetter::T> #this, self::Extension|set#fieldSetter::T value) → void;
+external static get Extension|staticFieldSetter() → core::int;
+external static set Extension|staticFieldSetter(core::int value) → void;
+static method test() → dynamic {
+  core::List<core::int> list = <core::int>[];
+  core::int value = self::Extension|get#field<core::int>(list);
+  self::Extension|set#field<core::int>(list, value);
+  value = self::Extension|get#finalField<core::int>(list);
+  value = self::Extension|method<core::int>(list);
+  value = self::Extension|get#getter<core::int>(list);
+  self::Extension|set#setter<core::int>(list, value);
+  value = self::Extension|get#property<core::int>(list);
+  self::Extension|set#property<core::int>(list, value);
+  value = self::Extension|get#fieldSetter<core::int>(list);
+  self::Extension|set#fieldSetter<core::int>(list, value);
+  core::List<core::int> iterable = list;
+  core::num n = self::Extension|get#field<core::num>(iterable);
+  self::Extension|set#field<core::num>(iterable, n);
+  n = self::Extension|get#finalField<core::num>(iterable);
+  n = self::Extension|method<core::num>(iterable);
+  n = self::Extension|get#getter<core::num>(iterable);
+  self::Extension|set#setter<core::num>(iterable, n);
+  n = self::Extension|get#property<core::num>(iterable);
+  self::Extension|set#property<core::num>(iterable, n);
+  n = self::Extension|get#fieldSetter<core::num>(iterable);
+  self::Extension|set#fieldSetter<core::num>(iterable, n);
+  value = self::Extension|staticField;
+  self::Extension|staticField = value;
+  value = self::Extension|staticFinalField;
+  value = self::Extension|staticMethod();
+  value = self::Extension|staticGetter;
+  self::Extension|staticSetter = value;
+  value = self::Extension|staticProperty;
+  self::Extension|staticProperty = value;
+  value = self::Extension|staticFieldSetter;
+  self::Extension|staticFieldSetter = value;
+}
+static method main() → dynamic {}
--- a/pkg/front_end/testcases/extensions/external.dart.weak.outline.expect
+++ b/pkg/front_end/testcases/extensions/external.dart.weak.outline.expect
@ -0,0 +1,53 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::num> on core::List<T> {
+  get field = self::Extension|get#field;
+  set field = self::Extension|set#field;
+  static get staticField = get self::Extension|staticField;
+  static set staticField = set self::Extension|staticField;
+  get finalField = self::Extension|get#finalField;
+  static get staticFinalField = get self::Extension|staticFinalField;
+  method method = self::Extension|method;
+  tearoff method = self::Extension|get#method;
+  static method staticMethod = self::Extension|staticMethod;
+  get getter = self::Extension|get#getter;
+  static get staticGetter = get self::Extension|staticGetter;
+  get property = self::Extension|get#property;
+  static get staticProperty = get self::Extension|staticProperty;
+  get fieldSetter = self::Extension|get#fieldSetter;
+  static get staticFieldSetter = get self::Extension|staticFieldSetter;
+  set setter = self::Extension|set#setter;
+  static set staticSetter = set self::Extension|staticSetter;
+  set property = self::Extension|set#property;
+  static set staticProperty = set self::Extension|staticProperty;
+  set fieldSetter = self::Extension|set#fieldSetter;
+  static set staticFieldSetter = set self::Extension|staticFieldSetter;
+}
+external static method Extension|get#field<T extends core::num>(core::List<self::Extension|get#field::T> #this) → self::Extension|get#field::T;
+external static method Extension|set#field<T extends core::num>(core::List<self::Extension|set#field::T> #this, self::Extension|set#field::T #externalFieldValue) → void;
+external static get Extension|staticField() → core::int;
+external static set Extension|staticField(core::int #externalFieldValue) → void;
+external static method Extension|get#finalField<T extends core::num>(core::List<self::Extension|get#finalField::T> #this) → self::Extension|get#finalField::T;
+external static get Extension|staticFinalField() → core::int;
+external static method Extension|method<T extends core::num>(lowered final core::List<self::Extension|method::T> #this) → self::Extension|method::T;
+static method Extension|get#method<T extends core::num>(lowered final core::List<self::Extension|get#method::T> #this) → () → self::Extension|get#method::T
+  return () → self::Extension|get#method::T => self::Extension|method<self::Extension|get#method::T>(#this);
+external static method Extension|staticMethod() → core::int;
+external static method Extension|get#getter<T extends core::num>(lowered final core::List<self::Extension|get#getter::T> #this) → self::Extension|get#getter::T;
+external static get Extension|staticGetter() → core::int;
+external static method Extension|set#setter<T extends core::num>(lowered final core::List<self::Extension|set#setter::T> #this, self::Extension|set#setter::T value) → void;
+external static set Extension|staticSetter(core::int value) → void;
+external static method Extension|get#property<T extends core::num>(lowered final core::List<self::Extension|get#property::T> #this) → self::Extension|get#property::T;
+external static method Extension|set#property<T extends core::num>(lowered final core::List<self::Extension|set#property::T> #this, self::Extension|set#property::T value) → void;
+external static get Extension|staticProperty() → core::int;
+external static set Extension|staticProperty(core::int value) → void;
+external static method Extension|get#fieldSetter<T extends core::num>(core::List<self::Extension|get#fieldSetter::T> #this) → self::Extension|get#fieldSetter::T;
+external static method Extension|set#fieldSetter<T extends core::num>(lowered final core::List<self::Extension|set#fieldSetter::T> #this, self::Extension|set#fieldSetter::T value) → void;
+external static get Extension|staticFieldSetter() → core::int;
+external static set Extension|staticFieldSetter(core::int value) → void;
+static method test() → dynamic
+  ;
+static method main() → dynamic
+  ;
--- a/pkg/front_end/testcases/extensions/external.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/extensions/external.dart.weak.transformed.expect
@ -0,0 +1,84 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::num> on core::List<T> {
+  get field = self::Extension|get#field;
+  set field = self::Extension|set#field;
+  static get staticField = get self::Extension|staticField;
+  static set staticField = set self::Extension|staticField;
+  get finalField = self::Extension|get#finalField;
+  static get staticFinalField = get self::Extension|staticFinalField;
+  method method = self::Extension|method;
+  tearoff method = self::Extension|get#method;
+  static method staticMethod = self::Extension|staticMethod;
+  get getter = self::Extension|get#getter;
+  static get staticGetter = get self::Extension|staticGetter;
+  get property = self::Extension|get#property;
+  static get staticProperty = get self::Extension|staticProperty;
+  get fieldSetter = self::Extension|get#fieldSetter;
+  static get staticFieldSetter = get self::Extension|staticFieldSetter;
+  set setter = self::Extension|set#setter;
+  static set staticSetter = set self::Extension|staticSetter;
+  set property = self::Extension|set#property;
+  static set staticProperty = set self::Extension|staticProperty;
+  set fieldSetter = self::Extension|set#fieldSetter;
+  static set staticFieldSetter = set self::Extension|staticFieldSetter;
+}
+external static method Extension|get#field<T extends core::num>(core::List<self::Extension|get#field::T> #this) → self::Extension|get#field::T;
+external static method Extension|set#field<T extends core::num>(core::List<self::Extension|set#field::T> #this, self::Extension|set#field::T #externalFieldValue) → void;
+external static get Extension|staticField() → core::int;
+external static set Extension|staticField(core::int #externalFieldValue) → void;
+external static method Extension|get#finalField<T extends core::num>(core::List<self::Extension|get#finalField::T> #this) → self::Extension|get#finalField::T;
+external static get Extension|staticFinalField() → core::int;
+external static method Extension|method<T extends core::num>(lowered final core::List<self::Extension|method::T> #this) → self::Extension|method::T;
+static method Extension|get#method<T extends core::num>(lowered final core::List<self::Extension|get#method::T> #this) → () → self::Extension|get#method::T
+  return () → self::Extension|get#method::T => self::Extension|method<self::Extension|get#method::T>(#this);
+external static method Extension|staticMethod() → core::int;
+external static method Extension|get#getter<T extends core::num>(lowered final core::List<self::Extension|get#getter::T> #this) → self::Extension|get#getter::T;
+external static get Extension|staticGetter() → core::int;
+external static method Extension|set#setter<T extends core::num>(lowered final core::List<self::Extension|set#setter::T> #this, self::Extension|set#setter::T value) → void;
+external static set Extension|staticSetter(core::int value) → void;
+external static method Extension|get#property<T extends core::num>(lowered final core::List<self::Extension|get#property::T> #this) → self::Extension|get#property::T;
+external static method Extension|set#property<T extends core::num>(lowered final core::List<self::Extension|set#property::T> #this, self::Extension|set#property::T value) → void;
+external static get Extension|staticProperty() → core::int;
+external static set Extension|staticProperty(core::int value) → void;
+external static method Extension|get#fieldSetter<T extends core::num>(core::List<self::Extension|get#fieldSetter::T> #this) → self::Extension|get#fieldSetter::T;
+external static method Extension|set#fieldSetter<T extends core::num>(lowered final core::List<self::Extension|set#fieldSetter::T> #this, self::Extension|set#fieldSetter::T value) → void;
+external static get Extension|staticFieldSetter() → core::int;
+external static set Extension|staticFieldSetter(core::int value) → void;
+static method test() → dynamic {
+  core::List<core::int> list = core::_GrowableList::•<core::int>(0);
+  core::int value = self::Extension|get#field<core::int>(list);
+  self::Extension|set#field<core::int>(list, value);
+  value = self::Extension|get#finalField<core::int>(list);
+  value = self::Extension|method<core::int>(list);
+  value = self::Extension|get#getter<core::int>(list);
+  self::Extension|set#setter<core::int>(list, value);
+  value = self::Extension|get#property<core::int>(list);
+  self::Extension|set#property<core::int>(list, value);
+  value = self::Extension|get#fieldSetter<core::int>(list);
+  self::Extension|set#fieldSetter<core::int>(list, value);
+  core::List<core::int> iterable = list;
+  core::num n = self::Extension|get#field<core::num>(iterable);
+  self::Extension|set#field<core::num>(iterable, n);
+  n = self::Extension|get#finalField<core::num>(iterable);
+  n = self::Extension|method<core::num>(iterable);
+  n = self::Extension|get#getter<core::num>(iterable);
+  self::Extension|set#setter<core::num>(iterable, n);
+  n = self::Extension|get#property<core::num>(iterable);
+  self::Extension|set#property<core::num>(iterable, n);
+  n = self::Extension|get#fieldSetter<core::num>(iterable);
+  self::Extension|set#fieldSetter<core::num>(iterable, n);
+  value = self::Extension|staticField;
+  self::Extension|staticField = value;
+  value = self::Extension|staticFinalField;
+  value = self::Extension|staticMethod();
+  value = self::Extension|staticGetter;
+  self::Extension|staticSetter = value;
+  value = self::Extension|staticProperty;
+  self::Extension|staticProperty = value;
+  value = self::Extension|staticFieldSetter;
+  self::Extension|staticFieldSetter = value;
+}
+static method main() → dynamic {}
--- a/pkg/front_end/testcases/nnbd/external_field_errors.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/external_field_errors.dart.strong.expect
@ -101,9 +101,9 @@ abstract class B extends core::Object /*isMixinDeclaration*/  {
  external static get finalStaticField() → core::int;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
@ -113,9 +113,9 @@ external static set topLevelField(core::int #externalFieldValue) → void;
 external static get finalTopLevelField() → core::int;
 external static get constField() → core::int;
 external static set constField(core::int #externalFieldValue) → void;
-external static get Extension|extensionInstanceField() → core::int;
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
 external static get Extension|extensionStaticField() → core::int;
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
 external static get Extension|finalExtensionStaticField() → core::int;
--- a/pkg/front_end/testcases/nnbd/external_field_errors.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/external_field_errors.dart.strong.transformed.expect
@ -101,9 +101,9 @@ abstract class B extends core::Object /*isMixinDeclaration*/  {
  external static get finalStaticField() → core::int;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
@ -113,9 +113,9 @@ external static set topLevelField(core::int #externalFieldValue) → void;
 external static get finalTopLevelField() → core::int;
 external static get constField() → core::int;
 external static set constField(core::int #externalFieldValue) → void;
-external static get Extension|extensionInstanceField() → core::int;
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
 external static get Extension|extensionStaticField() → core::int;
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
 external static get Extension|finalExtensionStaticField() → core::int;
--- a/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.expect
@ -101,9 +101,9 @@ abstract class B extends core::Object /*isMixinDeclaration*/  {
  external static get finalStaticField() → core::int;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
@ -113,9 +113,9 @@ external static set topLevelField(core::int #externalFieldValue) → void;
 external static get finalTopLevelField() → core::int;
 external static get constField() → core::int;
 external static set constField(core::int #externalFieldValue) → void;
-external static get Extension|extensionInstanceField() → core::int;
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
 external static get Extension|extensionStaticField() → core::int;
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
 external static get Extension|finalExtensionStaticField() → core::int;
--- a/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.outline.expect
+++ b/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.outline.expect
@ -21,9 +21,9 @@ abstract class B extends core::Object /*isMixinDeclaration*/  {
  external static get finalStaticField() → core::int;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
@ -33,9 +33,9 @@ external static set topLevelField(core::int #externalFieldValue) → void;
 external static get finalTopLevelField() → core::int;
 external static get constField() → core::int;
 external static set constField(core::int #externalFieldValue) → void;
-external static get Extension|extensionInstanceField() → core::int;
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
 external static get Extension|extensionStaticField() → core::int;
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
 external static get Extension|finalExtensionStaticField() → core::int;
--- a/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/external_field_errors.dart.weak.transformed.expect
@ -101,9 +101,9 @@ abstract class B extends core::Object /*isMixinDeclaration*/  {
  external static get finalStaticField() → core::int;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
@ -113,9 +113,9 @@ external static set topLevelField(core::int #externalFieldValue) → void;
 external static get finalTopLevelField() → core::int;
 external static get constField() → core::int;
 external static set constField(core::int #externalFieldValue) → void;
-external static get Extension|extensionInstanceField() → core::int;
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
 external static get Extension|extensionStaticField() → core::int;
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
 external static get Extension|finalExtensionStaticField() → core::int;
--- a/pkg/front_end/testcases/nnbd/external_fields.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/external_fields.dart.strong.expect
@ -78,15 +78,15 @@ class C extends core::Object implements self::A {
  external set untypedCovariantInstanceField(covariant dynamic #externalFieldValue) → void;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
-  get untypedExtensionInstanceField = get self::Extension|untypedExtensionInstanceField;
-  set untypedExtensionInstanceField = set self::Extension|untypedExtensionInstanceField;
-  get untypedFinalExtensionInstanceField = get self::Extension|untypedFinalExtensionInstanceField;
+  get untypedExtensionInstanceField = self::Extension|get#untypedExtensionInstanceField;
+  set untypedExtensionInstanceField = self::Extension|set#untypedExtensionInstanceField;
+  get untypedFinalExtensionInstanceField = self::Extension|get#untypedFinalExtensionInstanceField;
  static get untypedExtensionStaticField = get self::Extension|untypedExtensionStaticField;
  static set untypedExtensionStaticField = set self::Extension|untypedExtensionStaticField;
  static get untypedFinalExtensionStaticField = get self::Extension|untypedFinalExtensionStaticField;
@ -101,20 +101,20 @@ external static get untypedTopLevelField() → dynamic;
 external static set untypedTopLevelField(dynamic #externalFieldValue) → void;
 external static get untypedFinalTopLevelField() → dynamic;
@#C1
-external static get Extension|extensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
@#C1
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
@#C1
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
@#C1
 external static get Extension|extensionStaticField() → core::int;
@#C1
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
@#C1
 external static get Extension|finalExtensionStaticField() → core::int;
-external static get Extension|untypedExtensionInstanceField() → dynamic;
-external static set Extension|untypedExtensionInstanceField(dynamic #externalFieldValue) → void;
-external static get Extension|untypedFinalExtensionInstanceField() → dynamic;
+external static method Extension|get#untypedExtensionInstanceField(self::A #this) → dynamic;
+external static method Extension|set#untypedExtensionInstanceField(self::A #this, dynamic #externalFieldValue) → void;
+external static method Extension|get#untypedFinalExtensionInstanceField(self::A #this) → dynamic;
 external static get Extension|untypedExtensionStaticField() → dynamic;
 external static set Extension|untypedExtensionStaticField(dynamic #externalFieldValue) → void;
 external static get Extension|untypedFinalExtensionStaticField() → dynamic;
--- a/pkg/front_end/testcases/nnbd/external_fields.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/external_fields.dart.strong.transformed.expect
@ -78,15 +78,15 @@ class C extends core::Object implements self::A {
  external set untypedCovariantInstanceField(covariant dynamic #externalFieldValue) → void;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
-  get untypedExtensionInstanceField = get self::Extension|untypedExtensionInstanceField;
-  set untypedExtensionInstanceField = set self::Extension|untypedExtensionInstanceField;
-  get untypedFinalExtensionInstanceField = get self::Extension|untypedFinalExtensionInstanceField;
+  get untypedExtensionInstanceField = self::Extension|get#untypedExtensionInstanceField;
+  set untypedExtensionInstanceField = self::Extension|set#untypedExtensionInstanceField;
+  get untypedFinalExtensionInstanceField = self::Extension|get#untypedFinalExtensionInstanceField;
  static get untypedExtensionStaticField = get self::Extension|untypedExtensionStaticField;
  static set untypedExtensionStaticField = set self::Extension|untypedExtensionStaticField;
  static get untypedFinalExtensionStaticField = get self::Extension|untypedFinalExtensionStaticField;
@ -101,20 +101,20 @@ external static get untypedTopLevelField() → dynamic;
 external static set untypedTopLevelField(dynamic #externalFieldValue) → void;
 external static get untypedFinalTopLevelField() → dynamic;
@#C1
-external static get Extension|extensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
@#C1
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
@#C1
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
@#C1
 external static get Extension|extensionStaticField() → core::int;
@#C1
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
@#C1
 external static get Extension|finalExtensionStaticField() → core::int;
-external static get Extension|untypedExtensionInstanceField() → dynamic;
-external static set Extension|untypedExtensionInstanceField(dynamic #externalFieldValue) → void;
-external static get Extension|untypedFinalExtensionInstanceField() → dynamic;
+external static method Extension|get#untypedExtensionInstanceField(self::A #this) → dynamic;
+external static method Extension|set#untypedExtensionInstanceField(self::A #this, dynamic #externalFieldValue) → void;
+external static method Extension|get#untypedFinalExtensionInstanceField(self::A #this) → dynamic;
 external static get Extension|untypedExtensionStaticField() → dynamic;
 external static set Extension|untypedExtensionStaticField(dynamic #externalFieldValue) → void;
 external static get Extension|untypedFinalExtensionStaticField() → dynamic;
--- a/pkg/front_end/testcases/nnbd/external_fields.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/external_fields.dart.weak.expect
@ -78,15 +78,15 @@ class C extends core::Object implements self::A {
  external set untypedCovariantInstanceField(covariant dynamic #externalFieldValue) → void;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
-  get untypedExtensionInstanceField = get self::Extension|untypedExtensionInstanceField;
-  set untypedExtensionInstanceField = set self::Extension|untypedExtensionInstanceField;
-  get untypedFinalExtensionInstanceField = get self::Extension|untypedFinalExtensionInstanceField;
+  get untypedExtensionInstanceField = self::Extension|get#untypedExtensionInstanceField;
+  set untypedExtensionInstanceField = self::Extension|set#untypedExtensionInstanceField;
+  get untypedFinalExtensionInstanceField = self::Extension|get#untypedFinalExtensionInstanceField;
  static get untypedExtensionStaticField = get self::Extension|untypedExtensionStaticField;
  static set untypedExtensionStaticField = set self::Extension|untypedExtensionStaticField;
  static get untypedFinalExtensionStaticField = get self::Extension|untypedFinalExtensionStaticField;
@ -101,20 +101,20 @@ external static get untypedTopLevelField() → dynamic;
 external static set untypedTopLevelField(dynamic #externalFieldValue) → void;
 external static get untypedFinalTopLevelField() → dynamic;
@#C1
-external static get Extension|extensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
@#C1
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
@#C1
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
@#C1
 external static get Extension|extensionStaticField() → core::int;
@#C1
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
@#C1
 external static get Extension|finalExtensionStaticField() → core::int;
-external static get Extension|untypedExtensionInstanceField() → dynamic;
-external static set Extension|untypedExtensionInstanceField(dynamic #externalFieldValue) → void;
-external static get Extension|untypedFinalExtensionInstanceField() → dynamic;
+external static method Extension|get#untypedExtensionInstanceField(self::A #this) → dynamic;
+external static method Extension|set#untypedExtensionInstanceField(self::A #this, dynamic #externalFieldValue) → void;
+external static method Extension|get#untypedFinalExtensionInstanceField(self::A #this) → dynamic;
 external static get Extension|untypedExtensionStaticField() → dynamic;
 external static set Extension|untypedExtensionStaticField(dynamic #externalFieldValue) → void;
 external static get Extension|untypedFinalExtensionStaticField() → dynamic;
--- a/pkg/front_end/testcases/nnbd/external_fields.dart.weak.outline.expect
+++ b/pkg/front_end/testcases/nnbd/external_fields.dart.weak.outline.expect
@ -76,15 +76,15 @@ class C extends core::Object implements self::A {
  external set untypedCovariantInstanceField(covariant dynamic #externalFieldValue) → void;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
-  get untypedExtensionInstanceField = get self::Extension|untypedExtensionInstanceField;
-  set untypedExtensionInstanceField = set self::Extension|untypedExtensionInstanceField;
-  get untypedFinalExtensionInstanceField = get self::Extension|untypedFinalExtensionInstanceField;
+  get untypedExtensionInstanceField = self::Extension|get#untypedExtensionInstanceField;
+  set untypedExtensionInstanceField = self::Extension|set#untypedExtensionInstanceField;
+  get untypedFinalExtensionInstanceField = self::Extension|get#untypedFinalExtensionInstanceField;
  static get untypedExtensionStaticField = get self::Extension|untypedExtensionStaticField;
  static set untypedExtensionStaticField = set self::Extension|untypedExtensionStaticField;
  static get untypedFinalExtensionStaticField = get self::Extension|untypedFinalExtensionStaticField;
@ -99,20 +99,20 @@ external static get untypedTopLevelField() → dynamic;
 external static set untypedTopLevelField(dynamic #externalFieldValue) → void;
 external static get untypedFinalTopLevelField() → dynamic;
@self::Annotation::•()
-external static get Extension|extensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
@self::Annotation::•()
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
@self::Annotation::•()
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
@self::Annotation::•()
 external static get Extension|extensionStaticField() → core::int;
@self::Annotation::•()
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
@self::Annotation::•()
 external static get Extension|finalExtensionStaticField() → core::int;
-external static get Extension|untypedExtensionInstanceField() → dynamic;
-external static set Extension|untypedExtensionInstanceField(dynamic #externalFieldValue) → void;
-external static get Extension|untypedFinalExtensionInstanceField() → dynamic;
+external static method Extension|get#untypedExtensionInstanceField(self::A #this) → dynamic;
+external static method Extension|set#untypedExtensionInstanceField(self::A #this, dynamic #externalFieldValue) → void;
+external static method Extension|get#untypedFinalExtensionInstanceField(self::A #this) → dynamic;
 external static get Extension|untypedExtensionStaticField() → dynamic;
 external static set Extension|untypedExtensionStaticField(dynamic #externalFieldValue) → void;
 external static get Extension|untypedFinalExtensionStaticField() → dynamic;
--- a/pkg/front_end/testcases/nnbd/external_fields.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/external_fields.dart.weak.transformed.expect
@ -78,15 +78,15 @@ class C extends core::Object implements self::A {
  external set untypedCovariantInstanceField(covariant dynamic #externalFieldValue) → void;
 }
 extension Extension on self::A {
-  get extensionInstanceField = get self::Extension|extensionInstanceField;
-  set extensionInstanceField = set self::Extension|extensionInstanceField;
-  get finalExtensionInstanceField = get self::Extension|finalExtensionInstanceField;
+  get extensionInstanceField = self::Extension|get#extensionInstanceField;
+  set extensionInstanceField = self::Extension|set#extensionInstanceField;
+  get finalExtensionInstanceField = self::Extension|get#finalExtensionInstanceField;
  static get extensionStaticField = get self::Extension|extensionStaticField;
  static set extensionStaticField = set self::Extension|extensionStaticField;
  static get finalExtensionStaticField = get self::Extension|finalExtensionStaticField;
-  get untypedExtensionInstanceField = get self::Extension|untypedExtensionInstanceField;
-  set untypedExtensionInstanceField = set self::Extension|untypedExtensionInstanceField;
-  get untypedFinalExtensionInstanceField = get self::Extension|untypedFinalExtensionInstanceField;
+  get untypedExtensionInstanceField = self::Extension|get#untypedExtensionInstanceField;
+  set untypedExtensionInstanceField = self::Extension|set#untypedExtensionInstanceField;
+  get untypedFinalExtensionInstanceField = self::Extension|get#untypedFinalExtensionInstanceField;
  static get untypedExtensionStaticField = get self::Extension|untypedExtensionStaticField;
  static set untypedExtensionStaticField = set self::Extension|untypedExtensionStaticField;
  static get untypedFinalExtensionStaticField = get self::Extension|untypedFinalExtensionStaticField;
@ -101,20 +101,20 @@ external static get untypedTopLevelField() → dynamic;
 external static set untypedTopLevelField(dynamic #externalFieldValue) → void;
 external static get untypedFinalTopLevelField() → dynamic;
@#C1
-external static get Extension|extensionInstanceField() → core::int;
+external static method Extension|get#extensionInstanceField(self::A #this) → core::int;
@#C1
-external static set Extension|extensionInstanceField(core::int #externalFieldValue) → void;
+external static method Extension|set#extensionInstanceField(self::A #this, core::int #externalFieldValue) → void;
@#C1
-external static get Extension|finalExtensionInstanceField() → core::int;
+external static method Extension|get#finalExtensionInstanceField(self::A #this) → core::int;
@#C1
 external static get Extension|extensionStaticField() → core::int;
@#C1
 external static set Extension|extensionStaticField(core::int #externalFieldValue) → void;
@#C1
 external static get Extension|finalExtensionStaticField() → core::int;
-external static get Extension|untypedExtensionInstanceField() → dynamic;
-external static set Extension|untypedExtensionInstanceField(dynamic #externalFieldValue) → void;
-external static get Extension|untypedFinalExtensionInstanceField() → dynamic;
+external static method Extension|get#untypedExtensionInstanceField(self::A #this) → dynamic;
+external static method Extension|set#untypedExtensionInstanceField(self::A #this, dynamic #externalFieldValue) → void;
+external static method Extension|get#untypedFinalExtensionInstanceField(self::A #this) → dynamic;
 external static get Extension|untypedExtensionStaticField() → dynamic;
 external static set Extension|untypedExtensionStaticField(dynamic #externalFieldValue) → void;
 external static get Extension|untypedFinalExtensionStaticField() → dynamic;