diff --git a/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart b/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
index a4af6df..a036ae6 100644
--- a/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
@@ -2879,8 +2879,7 @@
 
   void check(ClassHierarchyBuilder hierarchy) {
     classBuilder.checkGetterSetter(hierarchy.types, getter.getMember(hierarchy),
-        setter.getMember(hierarchy),
-        isInterfaceCheck: !classBuilder.isMixinApplication);
+        setter.getMember(hierarchy));
   }
 }
 
diff --git a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
index 0899ab4..9dbff26 100644
--- a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
@@ -1126,8 +1126,7 @@
     // TODO(ahe): Handle other cases: accessors, operators, and fields.
   }
 
-  void checkGetterSetter(Types types, Member getter, Member setter,
-      {bool isInterfaceCheck = false}) {
+  void checkGetterSetter(Types types, Member getter, Member setter) {
     if (getter == setter) {
       return;
     }
diff --git a/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart b/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart
index b8d7b3d..867fb41 100644
--- a/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_extension_builder.dart
@@ -255,6 +255,14 @@
       } else if (builder is ProcedureBuilder) {
         // Check procedures
         library.checkTypesInProcedureBuilder(builder, typeEnvironment);
+        if (builder.isGetter) {
+          Builder setterDeclaration =
+              scope.lookupLocalMember(builder.name, setter: true);
+          if (setterDeclaration != null) {
+            library.checkGetterSetterTypes(
+                builder, setterDeclaration, typeEnvironment);
+          }
+        }
       } else {
         assert(false, "Unexpected member: $builder.");
       }
diff --git a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
index d142b10..0bd7da5 100644
--- a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
@@ -67,7 +67,7 @@
         findTypeArgumentIssuesForInvocation,
         getGenericTypeName;
 
-import 'package:kernel/type_algebra.dart' show substitute;
+import 'package:kernel/type_algebra.dart' show Substitution, substitute;
 
 import 'package:kernel/type_environment.dart'
     show SubtypeCheckMode, TypeEnvironment;
@@ -1610,6 +1610,100 @@
     return typeVariablesByName;
   }
 
+  void checkGetterSetterTypes(ProcedureBuilder getterBuilder,
+      ProcedureBuilder setterBuilder, TypeEnvironment typeEnvironment) {
+    DartType getterType;
+    List<TypeParameter> getterExtensionTypeParameters;
+    if (getterBuilder.isExtensionInstanceMember) {
+      // An extension instance getter
+      //
+      //     extension E<T> on A {
+      //       T get property => ...
+      //     }
+      //
+      // is encoded as a top level method
+      //
+      //   T# E#get#property<T#>(A #this) => ...
+      //
+      Procedure procedure = getterBuilder.procedure;
+      getterType = procedure.function.returnType;
+      getterExtensionTypeParameters = procedure.function.typeParameters;
+    } else {
+      getterType = getterBuilder.procedure.getterType;
+    }
+    DartType setterType;
+    if (setterBuilder.isExtensionInstanceMember) {
+      // An extension instance setter
+      //
+      //     extension E<T> on A {
+      //       void set property(T value) { ... }
+      //     }
+      //
+      // is encoded as a top level method
+      //
+      //   void E#set#property<T#>(A #this, T# value) { ... }
+      //
+      Procedure procedure = setterBuilder.procedure;
+      setterType = procedure.function.positionalParameters[1].type;
+      if (getterExtensionTypeParameters != null &&
+          getterExtensionTypeParameters.isNotEmpty) {
+        // We substitute the setter type parameters for the getter type
+        // parameters to check them below in a shared context.
+        List<TypeParameter> setterExtensionTypeParameters =
+            procedure.function.typeParameters;
+        assert(getterExtensionTypeParameters.length ==
+            setterExtensionTypeParameters.length);
+        setterType = Substitution.fromPairs(
+                setterExtensionTypeParameters,
+                new List<DartType>.generate(
+                    getterExtensionTypeParameters.length,
+                    (int index) => new TypeParameterType.forAlphaRenaming(
+                        setterExtensionTypeParameters[index],
+                        getterExtensionTypeParameters[index])))
+            .substituteType(setterType);
+      }
+    } else {
+      setterType = setterBuilder.procedure.setterType;
+    }
+
+    if (getterType is InvalidType || setterType is InvalidType) {
+      // Don't report a problem as something else is wrong that has already
+      // been reported.
+    } else {
+      bool isValid = typeEnvironment.isSubtypeOf(
+          getterType,
+          setterType,
+          library.isNonNullableByDefault
+              ? SubtypeCheckMode.withNullabilities
+              : SubtypeCheckMode.ignoringNullabilities);
+      if (!isValid && !library.isNonNullableByDefault) {
+        // Allow assignability in legacy libraries.
+        isValid = typeEnvironment.isSubtypeOf(
+            setterType, getterType, SubtypeCheckMode.ignoringNullabilities);
+      }
+      if (!isValid) {
+        String getterMemberName = getterBuilder.fullNameForErrors;
+        String setterMemberName = setterBuilder.fullNameForErrors;
+        Template<Message Function(DartType, String, DartType, String, bool)>
+            template = library.isNonNullableByDefault
+                ? templateInvalidGetterSetterType
+                : templateInvalidGetterSetterTypeLegacy;
+        addProblem(
+            template.withArguments(getterType, getterMemberName, setterType,
+                setterMemberName, library.isNonNullableByDefault),
+            getterBuilder.charOffset,
+            getterBuilder.name.length,
+            getterBuilder.fileUri,
+            context: [
+              templateInvalidGetterSetterTypeSetterContext
+                  .withArguments(setterMemberName)
+                  .withLocation(setterBuilder.fileUri, setterBuilder.charOffset,
+                      setterBuilder.name.length)
+            ]);
+      }
+    }
+  }
+
   void addExtensionDeclaration(
       String documentationComment,
       List<MetadataBuilder> metadata,
@@ -3579,6 +3673,14 @@
         checkTypesInField(declaration, typeEnvironment);
       } else if (declaration is ProcedureBuilder) {
         checkTypesInProcedureBuilder(declaration, typeEnvironment);
+        if (declaration.isGetter) {
+          Builder setterDeclaration =
+              scope.lookupLocalMember(declaration.name, setter: true);
+          if (setterDeclaration != null) {
+            checkGetterSetterTypes(
+                declaration, setterDeclaration, typeEnvironment);
+          }
+        }
       } else if (declaration is SourceClassBuilder) {
         declaration.checkTypesInOutline(typeEnvironment);
       } else if (declaration is SourceExtensionBuilder) {
diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index b3c7774..164bb07 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -508,6 +508,14 @@
 profile
 profiler
 propagated
+property2a
+property2b
+property4a
+property4b
+property5a
+property5b
+property8a
+property8b
 protected
 proved
 provider
diff --git a/pkg/front_end/testcases/extensions/extension_member_conflict.dart b/pkg/front_end/testcases/extensions/extension_member_conflict.dart
new file mode 100644
index 0000000..ef4e4de
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/extension_member_conflict.dart
@@ -0,0 +1,66 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+extension Extension<T> on int {
+  int get duplicateInstanceGetter => 0;
+  int get duplicateInstanceGetter => 0;
+
+  void set duplicateInstanceSetter(int value) {}
+  void set duplicateInstanceSetter(int value) {}
+
+  void duplicateInstanceMethod() {}
+  void duplicateInstanceMethod() {}
+
+  static int duplicateStaticField = 0;
+  static int duplicateStaticField = 0;
+
+  static int get duplicateStaticGetter => 0;
+  static int get duplicateStaticGetter => 0;
+
+  static void set duplicateStaticSetter(int value) {}
+  static void set duplicateStaticSetter(int value) {}
+
+  static void duplicateStaticMethod() {}
+  static void duplicateStaticMethod() {}
+
+  int get duplicateInstanceGetterPlusSetter => 0;
+  int get duplicateInstanceGetterPlusSetter => 0;
+  void set duplicateInstanceGetterPlusSetter(int value) {}
+
+  int get duplicateInstanceSetterPlusGetter => 0;
+  void set duplicateInstanceSetterPlusGetter(int value) {}
+  void set duplicateInstanceSetterPlusGetter(int value) {}
+
+  int get duplicateInstanceGetterAndSetter => 0;
+  int get duplicateInstanceGetterAndSetter => 0;
+  void set duplicateInstanceGetterAndSetter(int value) {}
+  void set duplicateInstanceGetterAndSetter(int value) {}
+
+  static int get duplicateStaticGetterPlusSetter => 0;
+  static int get duplicateStaticGetterPlusSetter => 0;
+  static void set duplicateStaticGetterPlusSetter(int value) {}
+
+  static int get duplicateStaticSetterPlusGetter => 0;
+  static void set duplicateStaticSetterPlusGetter(int value) {}
+  static void set duplicateStaticSetterPlusGetter(int value) {}
+
+  static int get duplicateStaticGetterAndSetter => 0;
+  static int get duplicateStaticGetterAndSetter => 0;
+  static void set duplicateStaticGetterAndSetter(int value) {}
+  static void set duplicateStaticGetterAndSetter(int value) {}
+
+  int get instanceGetterAndStaticSetter => 0;
+  static void set instanceGetterAndStaticSetter(int value) {}
+
+  static int get instanceSetterAndStaticGetter => 0;
+  void set instanceSetterAndStaticGetter(int value) {}
+
+  int get instanceGetterAndStaticField => 0;
+  static int instanceGetterAndStaticField = 0;
+
+  void set instanceSetterAndStaticField(int value) {}
+  static final int instanceGetterAndStaticField = 0;
+}
+
+main() {}
diff --git a/pkg/front_end/testcases/extensions/extension_member_conflict.dart.outline.expect b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.outline.expect
new file mode 100644
index 0000000..78e8afc
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.outline.expect
@@ -0,0 +1,223 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:7:11: Error: 'duplicateInstanceGetter' is already declared in this scope.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:6:11: Context: Previous declaration of 'duplicateInstanceGetter'.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:10:12: Error: 'duplicateInstanceSetter' is already declared in this scope.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:9:12: Context: Previous declaration of 'duplicateInstanceSetter'.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:13:8: Error: 'duplicateInstanceMethod' is already declared in this scope.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:12:8: Context: Previous declaration of 'duplicateInstanceMethod'.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:16:14: Error: 'duplicateStaticField' is already declared in this scope.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:15:14: Context: Previous declaration of 'duplicateStaticField'.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:19:18: Error: 'duplicateStaticGetter' is already declared in this scope.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:18:18: Context: Previous declaration of 'duplicateStaticGetter'.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:22:19: Error: 'duplicateStaticSetter' is already declared in this scope.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:21:19: Context: Previous declaration of 'duplicateStaticSetter'.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:25:15: Error: 'duplicateStaticMethod' is already declared in this scope.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:24:15: Context: Previous declaration of 'duplicateStaticMethod'.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:28:11: Error: 'duplicateInstanceGetterPlusSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:27:11: Context: Previous declaration of 'duplicateInstanceGetterPlusSetter'.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:33:12: Error: 'duplicateInstanceSetterPlusGetter' is already declared in this scope.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:32:12: Context: Previous declaration of 'duplicateInstanceSetterPlusGetter'.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:36:11: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:35:11: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:38:12: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:37:12: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:41:18: Error: 'duplicateStaticGetterPlusSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:40:18: Context: Previous declaration of 'duplicateStaticGetterPlusSetter'.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:46:19: Error: 'duplicateStaticSetterPlusGetter' is already declared in this scope.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:45:19: Context: Previous declaration of 'duplicateStaticSetterPlusGetter'.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:49:18: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:48:18: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:51:19: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:50:19: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:59:11: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   int get instanceGetterAndStaticField => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:63:20: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static final int instanceGetterAndStaticField = 0;
+//                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:54:19: Error: Conflicts with member 'instanceGetterAndStaticSetter'.
+//   static void set instanceGetterAndStaticSetter(int value) {}
+//                   ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:53:11: Error: Conflicts with setter 'instanceGetterAndStaticSetter'.
+//   int get instanceGetterAndStaticSetter => 0;
+//           ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:57:12: Error: Conflicts with member 'instanceSetterAndStaticGetter'.
+//   void set instanceSetterAndStaticGetter(int value) {}
+//            ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:56:18: Error: Conflicts with setter 'instanceSetterAndStaticGetter'.
+//   static int get instanceSetterAndStaticGetter => 0;
+//                  ^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::Object* = dynamic> on core::int* {
+  get duplicateInstanceGetter = self::Extension|get#duplicateInstanceGetter;
+  method duplicateInstanceMethod = self::Extension|duplicateInstanceMethod;
+  tearoff duplicateInstanceMethod = self::Extension|get#duplicateInstanceMethod;
+  static field duplicateStaticField = self::Extension|duplicateStaticField;
+  static get duplicateStaticGetter = get self::Extension|duplicateStaticGetter;
+  static method duplicateStaticMethod = self::Extension|duplicateStaticMethod;
+  get duplicateInstanceGetterPlusSetter = self::Extension|get#duplicateInstanceGetterPlusSetter;
+  get duplicateInstanceSetterPlusGetter = self::Extension|get#duplicateInstanceSetterPlusGetter;
+  get duplicateInstanceGetterAndSetter = self::Extension|get#duplicateInstanceGetterAndSetter;
+  static get duplicateStaticGetterPlusSetter = get self::Extension|duplicateStaticGetterPlusSetter;
+  static get duplicateStaticSetterPlusGetter = get self::Extension|duplicateStaticSetterPlusGetter;
+  static get duplicateStaticGetterAndSetter = get self::Extension|duplicateStaticGetterAndSetter;
+  get instanceGetterAndStaticSetter = self::Extension|get#instanceGetterAndStaticSetter;
+  static get instanceSetterAndStaticGetter = get self::Extension|instanceSetterAndStaticGetter;
+  get instanceGetterAndStaticField = self::Extension|get#instanceGetterAndStaticField;
+  set duplicateInstanceSetter = self::Extension|set#duplicateInstanceSetter;
+  static set duplicateStaticSetter = set self::Extension|duplicateStaticSetter;
+  set duplicateInstanceGetterPlusSetter = self::Extension|set#duplicateInstanceGetterPlusSetter;
+  set duplicateInstanceSetterPlusGetter = self::Extension|set#duplicateInstanceSetterPlusGetter;
+  set duplicateInstanceGetterAndSetter = self::Extension|set#duplicateInstanceGetterAndSetter;
+  static set duplicateStaticGetterPlusSetter = set self::Extension|duplicateStaticGetterPlusSetter;
+  static set duplicateStaticSetterPlusGetter = set self::Extension|duplicateStaticSetterPlusGetter;
+  static set duplicateStaticGetterAndSetter = set self::Extension|duplicateStaticGetterAndSetter;
+  static set instanceGetterAndStaticSetter = set self::Extension|instanceGetterAndStaticSetter;
+  set instanceSetterAndStaticGetter = self::Extension|set#instanceSetterAndStaticGetter;
+  set instanceSetterAndStaticField = self::Extension|set#instanceSetterAndStaticField;
+}
+static field core::int* Extension|duplicateStaticField;
+static method Extension|get#duplicateInstanceGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#duplicateInstanceSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static method Extension|duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → void
+  ;
+static method Extension|get#duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → () →* void
+  return () → void => self::Extension|duplicateInstanceMethod<self::Extension|get#duplicateInstanceMethod::T*>(#this);
+static get Extension|duplicateStaticGetter() → core::int*
+  ;
+static set Extension|duplicateStaticSetter(core::int* value) → void
+  ;
+static method Extension|duplicateStaticMethod() → void
+  ;
+static method Extension|get#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static method Extension|get#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static method Extension|get#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static get Extension|duplicateStaticGetterPlusSetter() → core::int*
+  ;
+static set Extension|duplicateStaticGetterPlusSetter(core::int* value) → void
+  ;
+static get Extension|duplicateStaticSetterPlusGetter() → core::int*
+  ;
+static set Extension|duplicateStaticSetterPlusGetter(core::int* value) → void
+  ;
+static get Extension|duplicateStaticGetterAndSetter() → core::int*
+  ;
+static set Extension|duplicateStaticGetterAndSetter(core::int* value) → void
+  ;
+static method Extension|get#instanceGetterAndStaticSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static set Extension|instanceGetterAndStaticSetter(core::int* value) → void
+  ;
+static get Extension|instanceSetterAndStaticGetter() → core::int*
+  ;
+static method Extension|set#instanceSetterAndStaticGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static method Extension|get#instanceGetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#instanceSetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void
+  ;
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.expect b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.expect
new file mode 100644
index 0000000..52aa6f4
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.expect
@@ -0,0 +1,209 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:7:11: Error: 'duplicateInstanceGetter' is already declared in this scope.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:6:11: Context: Previous declaration of 'duplicateInstanceGetter'.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:10:12: Error: 'duplicateInstanceSetter' is already declared in this scope.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:9:12: Context: Previous declaration of 'duplicateInstanceSetter'.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:13:8: Error: 'duplicateInstanceMethod' is already declared in this scope.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:12:8: Context: Previous declaration of 'duplicateInstanceMethod'.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:16:14: Error: 'duplicateStaticField' is already declared in this scope.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:15:14: Context: Previous declaration of 'duplicateStaticField'.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:19:18: Error: 'duplicateStaticGetter' is already declared in this scope.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:18:18: Context: Previous declaration of 'duplicateStaticGetter'.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:22:19: Error: 'duplicateStaticSetter' is already declared in this scope.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:21:19: Context: Previous declaration of 'duplicateStaticSetter'.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:25:15: Error: 'duplicateStaticMethod' is already declared in this scope.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:24:15: Context: Previous declaration of 'duplicateStaticMethod'.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:28:11: Error: 'duplicateInstanceGetterPlusSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:27:11: Context: Previous declaration of 'duplicateInstanceGetterPlusSetter'.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:33:12: Error: 'duplicateInstanceSetterPlusGetter' is already declared in this scope.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:32:12: Context: Previous declaration of 'duplicateInstanceSetterPlusGetter'.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:36:11: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:35:11: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:38:12: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:37:12: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:41:18: Error: 'duplicateStaticGetterPlusSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:40:18: Context: Previous declaration of 'duplicateStaticGetterPlusSetter'.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:46:19: Error: 'duplicateStaticSetterPlusGetter' is already declared in this scope.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:45:19: Context: Previous declaration of 'duplicateStaticSetterPlusGetter'.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:49:18: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:48:18: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:51:19: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:50:19: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:59:11: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   int get instanceGetterAndStaticField => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:63:20: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static final int instanceGetterAndStaticField = 0;
+//                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:54:19: Error: Conflicts with member 'instanceGetterAndStaticSetter'.
+//   static void set instanceGetterAndStaticSetter(int value) {}
+//                   ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:53:11: Error: Conflicts with setter 'instanceGetterAndStaticSetter'.
+//   int get instanceGetterAndStaticSetter => 0;
+//           ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:57:12: Error: Conflicts with member 'instanceSetterAndStaticGetter'.
+//   void set instanceSetterAndStaticGetter(int value) {}
+//            ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:56:18: Error: Conflicts with setter 'instanceSetterAndStaticGetter'.
+//   static int get instanceSetterAndStaticGetter => 0;
+//                  ^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::Object* = dynamic> on core::int* {
+  get duplicateInstanceGetter = self::Extension|get#duplicateInstanceGetter;
+  method duplicateInstanceMethod = self::Extension|duplicateInstanceMethod;
+  tearoff duplicateInstanceMethod = self::Extension|get#duplicateInstanceMethod;
+  static field duplicateStaticField = self::Extension|duplicateStaticField;
+  static get duplicateStaticGetter = get self::Extension|duplicateStaticGetter;
+  static method duplicateStaticMethod = self::Extension|duplicateStaticMethod;
+  get duplicateInstanceGetterPlusSetter = self::Extension|get#duplicateInstanceGetterPlusSetter;
+  get duplicateInstanceSetterPlusGetter = self::Extension|get#duplicateInstanceSetterPlusGetter;
+  get duplicateInstanceGetterAndSetter = self::Extension|get#duplicateInstanceGetterAndSetter;
+  static get duplicateStaticGetterPlusSetter = get self::Extension|duplicateStaticGetterPlusSetter;
+  static get duplicateStaticSetterPlusGetter = get self::Extension|duplicateStaticSetterPlusGetter;
+  static get duplicateStaticGetterAndSetter = get self::Extension|duplicateStaticGetterAndSetter;
+  get instanceGetterAndStaticSetter = self::Extension|get#instanceGetterAndStaticSetter;
+  static get instanceSetterAndStaticGetter = get self::Extension|instanceSetterAndStaticGetter;
+  get instanceGetterAndStaticField = self::Extension|get#instanceGetterAndStaticField;
+  set duplicateInstanceSetter = self::Extension|set#duplicateInstanceSetter;
+  static set duplicateStaticSetter = set self::Extension|duplicateStaticSetter;
+  set duplicateInstanceGetterPlusSetter = self::Extension|set#duplicateInstanceGetterPlusSetter;
+  set duplicateInstanceSetterPlusGetter = self::Extension|set#duplicateInstanceSetterPlusGetter;
+  set duplicateInstanceGetterAndSetter = self::Extension|set#duplicateInstanceGetterAndSetter;
+  static set duplicateStaticGetterPlusSetter = set self::Extension|duplicateStaticGetterPlusSetter;
+  static set duplicateStaticSetterPlusGetter = set self::Extension|duplicateStaticSetterPlusGetter;
+  static set duplicateStaticGetterAndSetter = set self::Extension|duplicateStaticGetterAndSetter;
+  static set instanceGetterAndStaticSetter = set self::Extension|instanceGetterAndStaticSetter;
+  set instanceSetterAndStaticGetter = self::Extension|set#instanceSetterAndStaticGetter;
+  set instanceSetterAndStaticField = self::Extension|set#instanceSetterAndStaticField;
+}
+static field core::int* Extension|duplicateStaticField;
+static method Extension|get#duplicateInstanceGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → void {}
+static method Extension|get#duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → () →* void
+  return () → void => self::Extension|duplicateInstanceMethod<self::Extension|get#duplicateInstanceMethod::T*>(#this);
+static get Extension|duplicateStaticGetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticSetter(core::int* value) → void {}
+static method Extension|duplicateStaticMethod() → void {}
+static method Extension|get#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static get Extension|duplicateStaticGetterPlusSetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticGetterPlusSetter(core::int* value) → void {}
+static get Extension|duplicateStaticSetterPlusGetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticSetterPlusGetter(core::int* value) → void {}
+static get Extension|duplicateStaticGetterAndSetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticGetterAndSetter(core::int* value) → void {}
+static method Extension|get#instanceGetterAndStaticSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static set Extension|instanceGetterAndStaticSetter(core::int* value) → void {}
+static get Extension|instanceSetterAndStaticGetter() → core::int*
+  return 0;
+static method Extension|set#instanceSetterAndStaticGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#instanceGetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#instanceSetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.transformed.expect
new file mode 100644
index 0000000..52aa6f4
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.strong.transformed.expect
@@ -0,0 +1,209 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:7:11: Error: 'duplicateInstanceGetter' is already declared in this scope.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:6:11: Context: Previous declaration of 'duplicateInstanceGetter'.
+//   int get duplicateInstanceGetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:10:12: Error: 'duplicateInstanceSetter' is already declared in this scope.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:9:12: Context: Previous declaration of 'duplicateInstanceSetter'.
+//   void set duplicateInstanceSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:13:8: Error: 'duplicateInstanceMethod' is already declared in this scope.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:12:8: Context: Previous declaration of 'duplicateInstanceMethod'.
+//   void duplicateInstanceMethod() {}
+//        ^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:16:14: Error: 'duplicateStaticField' is already declared in this scope.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:15:14: Context: Previous declaration of 'duplicateStaticField'.
+//   static int duplicateStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:19:18: Error: 'duplicateStaticGetter' is already declared in this scope.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:18:18: Context: Previous declaration of 'duplicateStaticGetter'.
+//   static int get duplicateStaticGetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:22:19: Error: 'duplicateStaticSetter' is already declared in this scope.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:21:19: Context: Previous declaration of 'duplicateStaticSetter'.
+//   static void set duplicateStaticSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:25:15: Error: 'duplicateStaticMethod' is already declared in this scope.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:24:15: Context: Previous declaration of 'duplicateStaticMethod'.
+//   static void duplicateStaticMethod() {}
+//               ^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:28:11: Error: 'duplicateInstanceGetterPlusSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:27:11: Context: Previous declaration of 'duplicateInstanceGetterPlusSetter'.
+//   int get duplicateInstanceGetterPlusSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:33:12: Error: 'duplicateInstanceSetterPlusGetter' is already declared in this scope.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:32:12: Context: Previous declaration of 'duplicateInstanceSetterPlusGetter'.
+//   void set duplicateInstanceSetterPlusGetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:36:11: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:35:11: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   int get duplicateInstanceGetterAndSetter => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:38:12: Error: 'duplicateInstanceGetterAndSetter' is already declared in this scope.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:37:12: Context: Previous declaration of 'duplicateInstanceGetterAndSetter'.
+//   void set duplicateInstanceGetterAndSetter(int value) {}
+//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:41:18: Error: 'duplicateStaticGetterPlusSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:40:18: Context: Previous declaration of 'duplicateStaticGetterPlusSetter'.
+//   static int get duplicateStaticGetterPlusSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:46:19: Error: 'duplicateStaticSetterPlusGetter' is already declared in this scope.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:45:19: Context: Previous declaration of 'duplicateStaticSetterPlusGetter'.
+//   static void set duplicateStaticSetterPlusGetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:49:18: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:48:18: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static int get duplicateStaticGetterAndSetter => 0;
+//                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:51:19: Error: 'duplicateStaticGetterAndSetter' is already declared in this scope.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:50:19: Context: Previous declaration of 'duplicateStaticGetterAndSetter'.
+//   static void set duplicateStaticGetterAndSetter(int value) {}
+//                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:59:11: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   int get instanceGetterAndStaticField => 0;
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:63:20: Error: 'instanceGetterAndStaticField' is already declared in this scope.
+//   static final int instanceGetterAndStaticField = 0;
+//                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:60:14: Context: Previous declaration of 'instanceGetterAndStaticField'.
+//   static int instanceGetterAndStaticField = 0;
+//              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:54:19: Error: Conflicts with member 'instanceGetterAndStaticSetter'.
+//   static void set instanceGetterAndStaticSetter(int value) {}
+//                   ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:53:11: Error: Conflicts with setter 'instanceGetterAndStaticSetter'.
+//   int get instanceGetterAndStaticSetter => 0;
+//           ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:57:12: Error: Conflicts with member 'instanceSetterAndStaticGetter'.
+//   void set instanceSetterAndStaticGetter(int value) {}
+//            ^
+//
+// pkg/front_end/testcases/extensions/extension_member_conflict.dart:56:18: Error: Conflicts with setter 'instanceSetterAndStaticGetter'.
+//   static int get instanceSetterAndStaticGetter => 0;
+//                  ^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Extension<T extends core::Object* = dynamic> on core::int* {
+  get duplicateInstanceGetter = self::Extension|get#duplicateInstanceGetter;
+  method duplicateInstanceMethod = self::Extension|duplicateInstanceMethod;
+  tearoff duplicateInstanceMethod = self::Extension|get#duplicateInstanceMethod;
+  static field duplicateStaticField = self::Extension|duplicateStaticField;
+  static get duplicateStaticGetter = get self::Extension|duplicateStaticGetter;
+  static method duplicateStaticMethod = self::Extension|duplicateStaticMethod;
+  get duplicateInstanceGetterPlusSetter = self::Extension|get#duplicateInstanceGetterPlusSetter;
+  get duplicateInstanceSetterPlusGetter = self::Extension|get#duplicateInstanceSetterPlusGetter;
+  get duplicateInstanceGetterAndSetter = self::Extension|get#duplicateInstanceGetterAndSetter;
+  static get duplicateStaticGetterPlusSetter = get self::Extension|duplicateStaticGetterPlusSetter;
+  static get duplicateStaticSetterPlusGetter = get self::Extension|duplicateStaticSetterPlusGetter;
+  static get duplicateStaticGetterAndSetter = get self::Extension|duplicateStaticGetterAndSetter;
+  get instanceGetterAndStaticSetter = self::Extension|get#instanceGetterAndStaticSetter;
+  static get instanceSetterAndStaticGetter = get self::Extension|instanceSetterAndStaticGetter;
+  get instanceGetterAndStaticField = self::Extension|get#instanceGetterAndStaticField;
+  set duplicateInstanceSetter = self::Extension|set#duplicateInstanceSetter;
+  static set duplicateStaticSetter = set self::Extension|duplicateStaticSetter;
+  set duplicateInstanceGetterPlusSetter = self::Extension|set#duplicateInstanceGetterPlusSetter;
+  set duplicateInstanceSetterPlusGetter = self::Extension|set#duplicateInstanceSetterPlusGetter;
+  set duplicateInstanceGetterAndSetter = self::Extension|set#duplicateInstanceGetterAndSetter;
+  static set duplicateStaticGetterPlusSetter = set self::Extension|duplicateStaticGetterPlusSetter;
+  static set duplicateStaticSetterPlusGetter = set self::Extension|duplicateStaticSetterPlusGetter;
+  static set duplicateStaticGetterAndSetter = set self::Extension|duplicateStaticGetterAndSetter;
+  static set instanceGetterAndStaticSetter = set self::Extension|instanceGetterAndStaticSetter;
+  set instanceSetterAndStaticGetter = self::Extension|set#instanceSetterAndStaticGetter;
+  set instanceSetterAndStaticField = self::Extension|set#instanceSetterAndStaticField;
+}
+static field core::int* Extension|duplicateStaticField;
+static method Extension|get#duplicateInstanceGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → void {}
+static method Extension|get#duplicateInstanceMethod<T extends core::Object* = dynamic>(final core::int* #this) → () →* void
+  return () → void => self::Extension|duplicateInstanceMethod<self::Extension|get#duplicateInstanceMethod::T*>(#this);
+static get Extension|duplicateStaticGetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticSetter(core::int* value) → void {}
+static method Extension|duplicateStaticMethod() → void {}
+static method Extension|get#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceGetterPlusSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceSetterPlusGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#duplicateInstanceGetterAndSetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static get Extension|duplicateStaticGetterPlusSetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticGetterPlusSetter(core::int* value) → void {}
+static get Extension|duplicateStaticSetterPlusGetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticSetterPlusGetter(core::int* value) → void {}
+static get Extension|duplicateStaticGetterAndSetter() → core::int*
+  return 0;
+static set Extension|duplicateStaticGetterAndSetter(core::int* value) → void {}
+static method Extension|get#instanceGetterAndStaticSetter<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static set Extension|instanceGetterAndStaticSetter(core::int* value) → void {}
+static get Extension|instanceSetterAndStaticGetter() → core::int*
+  return 0;
+static method Extension|set#instanceSetterAndStaticGetter<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method Extension|get#instanceGetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#instanceSetterAndStaticField<T extends core::Object* = dynamic>(final core::int* #this, core::int* value) → void {}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/extensions/extension_member_conflict.dart.textual_outline.expect b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.textual_outline.expect
new file mode 100644
index 0000000..6d262f3
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/extension_member_conflict.dart.textual_outline.expect
@@ -0,0 +1,3 @@
+extension Extension<T> (){}
+on int (){}
+main() {}
diff --git a/pkg/front_end/testcases/general/getter_vs_setter_type.dart b/pkg/front_end/testcases/general/getter_vs_setter_type.dart
index 2f92b93..4be746d 100644
--- a/pkg/front_end/testcases/general/getter_vs_setter_type.dart
+++ b/pkg/front_end/testcases/general/getter_vs_setter_type.dart
@@ -6,8 +6,11 @@
   int get property1; // ok
   void set property1(int i);
 
-  int get property2; // ok
-  void set property2(int i);
+  num get property2a; // ok
+  void set property2a(int i);
+
+  int get property2b; // ok
+  void set property2b(num i);
 
   String get property3; // error
   void set property3(int i);
@@ -17,6 +20,18 @@
   int property5; // ok
 
   covariant String property6; // ok
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8a => 0; // ok
+  static void set property8a(num value) {}
+
+  static num get property8b => 0; // ok
+  static void set property8b(int value) {}
+
+  static num get property9 => 0; // error
+  static void set property9(String value) {}
 }
 
 abstract class B1 {
@@ -102,4 +117,42 @@
 abstract class D4
     implements D3 /* no need for error on property2 and property3 */ {}
 
+extension Extension<T extends num, S extends T> on int {
+  int get property1 => 0; // ok
+  void set property1(int i) {}
+
+  num get property2a => 0; // ok
+  void set property2a(int i) {}
+
+  int get property2b => 0; // ok
+  void set property2b(num i) {}
+
+  String get property3 => ''; // error
+  void set property3(int i) {}
+
+  S get property4 => 0; // ok
+  void set property4(S i) {}
+
+  S get property5a => 0; // ok
+  void set property5a(T i) {}
+
+  T get property5b => 0; // ok
+  void set property5b(S i) {}
+
+  String get property6 => ''; // error
+  void set property6(S i) {}
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8a => 0; // ok
+  static void set property8a(num value) {}
+
+  static num get property8b => 0; // ok
+  static void set property8b(int value) {}
+
+  static num get property9 => 0; // error
+  static void set property9(String value) {}
+}
+
 main() {}
diff --git a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.outline.expect b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.outline.expect
index d0db1ea..f255528 100644
--- a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.outline.expect
+++ b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.outline.expect
@@ -2,125 +2,153 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:12:14: Error: The type 'String' of the getter 'A.property3' is not assignable to the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:15:14: Error: The type 'String' of the getter 'A.property3' is not assignable to the type 'int' of the setter 'A.property3'.
 //   String get property3; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:13:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:41:12: Error: The type 'int' of the inherited getter 'B1.property2' is not assignable to the type 'String' of the setter 'B2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:33:18: Error: The type 'num' of the getter 'A.property9' is not assignable to the type 'String' of the setter 'A.property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:34:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(String value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:56:12: Error: The type 'int' of the inherited getter 'B1.property2' is not assignable to the type 'String' of the setter 'B2.property2'.
 //   void set property2(String i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:25:11: Context: This is the declaration of the getter 'B1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:40:11: Context: This is the declaration of the getter 'B1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:43:12: Error: The type 'String' of the inherited getter 'B1.property3' is not assignable to the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:58:12: Error: The type 'String' of the inherited getter 'B1.property3' is not assignable to the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:27:14: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:42:14: Context: This is the declaration of the getter 'B1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:47:12: Error: The type 'int' of the inherited field 'B1.property5' is not assignable to the type 'String' of the setter 'B2.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:62:12: Error: The type 'int' of the inherited field 'B1.property5' is not assignable to the type 'String' of the setter 'B2.property5'.
 //   void set property5(String i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:31:13: Context: This is the declaration of the field 'B1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:46:13: Context: This is the declaration of the field 'B1.property5'.
 //   final int property5;
 //             ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:49:12: Error: The type 'String' of the inherited field 'B1.property6' is not assignable to the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:64:12: Error: The type 'String' of the inherited field 'B1.property6' is not assignable to the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:33:16: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:48:16: Context: This is the declaration of the field 'B1.property6'.
 //   final String property6;
 //                ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:69:11: Error: The type 'int' of the getter 'C2.property2' is not assignable to the type 'String' of the inherited setter 'C1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:84:11: Error: The type 'int' of the getter 'C2.property2' is not assignable to the type 'String' of the inherited setter 'C1.property2'.
 //   int get property2; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:55:12: Context: This is the declaration of the setter 'C1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:70:12: Context: This is the declaration of the setter 'C1.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:71:14: Error: The type 'String' of the getter 'C2.property3' is not assignable to the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:86:14: Error: The type 'String' of the getter 'C2.property3' is not assignable to the type 'int' of the inherited setter 'C1.property3'.
 //   String get property3; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:57:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:72:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:77:11: Error: The return type of the method 'C2.property5' is 'int', which does not match the return type, 'String', of the overridden method, 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:92:11: Error: The return type of the method 'C2.property5' is 'int', which does not match the return type, 'String', of the overridden method, 'C1.property5'.
 // Change to a subtype of 'String'.
 //   int get property5; // error
 //           ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:61:10: Context: This is the overridden method ('property5').
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:76:10: Context: This is the overridden method ('property5').
 //   String property5;
 //          ^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:77:11: Error: The type 'int' of the getter 'C2.property5' is not assignable to the type 'String' of the inherited setter 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:92:11: Error: The type 'int' of the getter 'C2.property5' is not assignable to the type 'String' of the inherited setter 'C1.property5'.
 //   int get property5; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:61:10: Context: This is the declaration of the setter 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:76:10: Context: This is the declaration of the setter 'C1.property5'.
 //   String property5;
 //          ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:81:14: Error: The return type of the method 'C2.property6' is 'String', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:96:14: Error: The return type of the method 'C2.property6' is 'String', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   String get property6; // error
 //              ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:63:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:78:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:81:14: Error: The type 'String' of the getter 'C2.property6' is not assignable to the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:96:14: Error: The type 'String' of the getter 'C2.property6' is not assignable to the type 'int' of the inherited setter 'C1.property6'.
 //   String get property6; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:63:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:78:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:100:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:115:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
 // abstract class D3 implements D1, D2 /* error on property2 and property3 */ {}
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:11: Context: This is the declaration of the getter 'D1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:110:12: Context: This is the declaration of the setter 'D2.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:100:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:115:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property2 and property3 */ {}
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:89:14: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:104:14: Context: This is the declaration of the getter 'D1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:97:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:112:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:117:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
 // abstract class D4
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:11: Context: This is the declaration of the getter 'D1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:110:12: Context: This is the declaration of the setter 'D2.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:117:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:89:14: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:104:14: Context: This is the declaration of the getter 'D1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:97:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:112:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:130:14: Error: The type 'String' of the getter 'property3' is not assignable to the type 'int' of the setter 'property3'.
+//   String get property3 => ''; // error
+//              ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:131:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:142:14: Error: The type 'String' of the getter 'property6' is not assignable to the type 'S' of the setter 'property6'.
+//   String get property6 => ''; // error
+//              ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:143:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(S i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:154:18: Error: The type 'num' of the getter 'property9' is not assignable to the type 'String' of the setter 'property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:155:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(String value) {}
+//                   ^^^^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -132,10 +160,28 @@
     ;
   abstract get property1() → core::int*;
   abstract set property1(core::int* i) → void;
-  abstract get property2() → core::int*;
-  abstract set property2(core::int* i) → void;
+  abstract get property2a() → core::num*;
+  abstract set property2a(core::int* i) → void;
+  abstract get property2b() → core::int*;
+  abstract set property2b(core::num* i) → void;
   abstract get property3() → core::String*;
   abstract set property3(core::int* i) → void;
+  static get property7() → core::int*
+    ;
+  static set property7(core::int* value) → void
+    ;
+  static get property8a() → core::int*
+    ;
+  static set property8a(core::num* value) → void
+    ;
+  static get property8b() → core::num*
+    ;
+  static set property8b(core::int* value) → void
+    ;
+  static get property9() → core::num*
+    ;
+  static set property9(core::String* value) → void
+    ;
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
@@ -289,5 +335,79 @@
   abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
   abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
 }
+extension Extension<T extends core::num* = core::num*, S extends T* = core::num*> on core::int* {
+  get property1 = self::Extension|get#property1;
+  get property2a = self::Extension|get#property2a;
+  get property2b = self::Extension|get#property2b;
+  get property3 = self::Extension|get#property3;
+  get property4 = self::Extension|get#property4;
+  get property5a = self::Extension|get#property5a;
+  get property5b = self::Extension|get#property5b;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8a = get self::Extension|property8a;
+  static get property8b = get self::Extension|property8b;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2a = self::Extension|set#property2a;
+  set property2b = self::Extension|set#property2b;
+  set property3 = self::Extension|set#property3;
+  set property4 = self::Extension|set#property4;
+  set property5a = self::Extension|set#property5a;
+  set property5b = self::Extension|set#property5b;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8a = set self::Extension|property8a;
+  static set property8b = set self::Extension|property8b;
+  static set property9 = set self::Extension|property9;
+}
+static method Extension|get#property1<T extends core::num* = core::num*, S extends self::Extension|get#property1::T* = core::num*>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#property1<T extends core::num* = core::num*, S extends self::Extension|set#property1::T* = core::num*>(final core::int* #this, core::int* i) → void
+  ;
+static method Extension|get#property2a<T extends core::num* = core::num*, S extends self::Extension|get#property2a::T* = core::num*>(final core::int* #this) → core::num*
+  ;
+static method Extension|set#property2a<T extends core::num* = core::num*, S extends self::Extension|set#property2a::T* = core::num*>(final core::int* #this, core::int* i) → void
+  ;
+static method Extension|get#property2b<T extends core::num* = core::num*, S extends self::Extension|get#property2b::T* = core::num*>(final core::int* #this) → core::int*
+  ;
+static method Extension|set#property2b<T extends core::num* = core::num*, S extends self::Extension|set#property2b::T* = core::num*>(final core::int* #this, core::num* i) → void
+  ;
+static method Extension|get#property3<T extends core::num* = core::num*, S extends self::Extension|get#property3::T* = core::num*>(final core::int* #this) → core::String*
+  ;
+static method Extension|set#property3<T extends core::num* = core::num*, S extends self::Extension|set#property3::T* = core::num*>(final core::int* #this, core::int* i) → void
+  ;
+static method Extension|get#property4<T extends core::num* = core::num*, S extends self::Extension|get#property4::T* = core::num*>(final core::int* #this) → self::Extension|get#property4::S*
+  ;
+static method Extension|set#property4<T extends core::num* = core::num*, S extends self::Extension|set#property4::T* = core::num*>(final core::int* #this, self::Extension|set#property4::S* i) → void
+  ;
+static method Extension|get#property5a<T extends core::num* = core::num*, S extends self::Extension|get#property5a::T* = core::num*>(final core::int* #this) → self::Extension|get#property5a::S*
+  ;
+static method Extension|set#property5a<T extends core::num* = core::num*, S extends self::Extension|set#property5a::T* = core::num*>(final core::int* #this, self::Extension|set#property5a::T* i) → void
+  ;
+static method Extension|get#property5b<T extends core::num* = core::num*, S extends self::Extension|get#property5b::T* = core::num*>(final core::int* #this) → self::Extension|get#property5b::T*
+  ;
+static method Extension|set#property5b<T extends core::num* = core::num*, S extends self::Extension|set#property5b::T* = core::num*>(final core::int* #this, self::Extension|set#property5b::S* i) → void
+  ;
+static method Extension|get#property6<T extends core::num* = core::num*, S extends self::Extension|get#property6::T* = core::num*>(final core::int* #this) → core::String*
+  ;
+static method Extension|set#property6<T extends core::num* = core::num*, S extends self::Extension|set#property6::T* = core::num*>(final core::int* #this, self::Extension|set#property6::S* i) → void
+  ;
+static get Extension|property7() → core::int*
+  ;
+static set Extension|property7(core::int* value) → void
+  ;
+static get Extension|property8a() → core::int*
+  ;
+static set Extension|property8a(core::num* value) → void
+  ;
+static get Extension|property8b() → core::num*
+  ;
+static set Extension|property8b(core::int* value) → void
+  ;
+static get Extension|property9() → core::num*
+  ;
+static set Extension|property9(core::String* value) → void
+  ;
 static method main() → dynamic
   ;
diff --git a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.strong.expect b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.strong.expect
index eb497ad..0ab82ac 100644
--- a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.strong.expect
+++ b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.strong.expect
@@ -2,125 +2,165 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:12:14: Error: The type 'String' of the getter 'A.property3' is not assignable to the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:15:14: Error: The type 'String' of the getter 'A.property3' is not assignable to the type 'int' of the setter 'A.property3'.
 //   String get property3; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:13:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:41:12: Error: The type 'int' of the inherited getter 'B1.property2' is not assignable to the type 'String' of the setter 'B2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:33:18: Error: The type 'num' of the getter 'A.property9' is not assignable to the type 'String' of the setter 'A.property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:34:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(String value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:56:12: Error: The type 'int' of the inherited getter 'B1.property2' is not assignable to the type 'String' of the setter 'B2.property2'.
 //   void set property2(String i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:25:11: Context: This is the declaration of the getter 'B1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:40:11: Context: This is the declaration of the getter 'B1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:43:12: Error: The type 'String' of the inherited getter 'B1.property3' is not assignable to the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:58:12: Error: The type 'String' of the inherited getter 'B1.property3' is not assignable to the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:27:14: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:42:14: Context: This is the declaration of the getter 'B1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:47:12: Error: The type 'int' of the inherited field 'B1.property5' is not assignable to the type 'String' of the setter 'B2.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:62:12: Error: The type 'int' of the inherited field 'B1.property5' is not assignable to the type 'String' of the setter 'B2.property5'.
 //   void set property5(String i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:31:13: Context: This is the declaration of the field 'B1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:46:13: Context: This is the declaration of the field 'B1.property5'.
 //   final int property5;
 //             ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:49:12: Error: The type 'String' of the inherited field 'B1.property6' is not assignable to the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:64:12: Error: The type 'String' of the inherited field 'B1.property6' is not assignable to the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:33:16: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:48:16: Context: This is the declaration of the field 'B1.property6'.
 //   final String property6;
 //                ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:69:11: Error: The type 'int' of the getter 'C2.property2' is not assignable to the type 'String' of the inherited setter 'C1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:84:11: Error: The type 'int' of the getter 'C2.property2' is not assignable to the type 'String' of the inherited setter 'C1.property2'.
 //   int get property2; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:55:12: Context: This is the declaration of the setter 'C1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:70:12: Context: This is the declaration of the setter 'C1.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:71:14: Error: The type 'String' of the getter 'C2.property3' is not assignable to the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:86:14: Error: The type 'String' of the getter 'C2.property3' is not assignable to the type 'int' of the inherited setter 'C1.property3'.
 //   String get property3; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:57:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:72:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:77:11: Error: The return type of the method 'C2.property5' is 'int', which does not match the return type, 'String', of the overridden method, 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:92:11: Error: The return type of the method 'C2.property5' is 'int', which does not match the return type, 'String', of the overridden method, 'C1.property5'.
 // Change to a subtype of 'String'.
 //   int get property5; // error
 //           ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:61:10: Context: This is the overridden method ('property5').
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:76:10: Context: This is the overridden method ('property5').
 //   String property5;
 //          ^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:77:11: Error: The type 'int' of the getter 'C2.property5' is not assignable to the type 'String' of the inherited setter 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:92:11: Error: The type 'int' of the getter 'C2.property5' is not assignable to the type 'String' of the inherited setter 'C1.property5'.
 //   int get property5; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:61:10: Context: This is the declaration of the setter 'C1.property5'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:76:10: Context: This is the declaration of the setter 'C1.property5'.
 //   String property5;
 //          ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:81:14: Error: The return type of the method 'C2.property6' is 'String', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:96:14: Error: The return type of the method 'C2.property6' is 'String', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   String get property6; // error
 //              ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:63:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:78:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:81:14: Error: The type 'String' of the getter 'C2.property6' is not assignable to the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:96:14: Error: The type 'String' of the getter 'C2.property6' is not assignable to the type 'int' of the inherited setter 'C1.property6'.
 //   String get property6; // error
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:63:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:78:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:100:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:115:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
 // abstract class D3 implements D1, D2 /* error on property2 and property3 */ {}
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:11: Context: This is the declaration of the getter 'D1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:110:12: Context: This is the declaration of the setter 'D2.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:100:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:115:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property2 and property3 */ {}
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:89:14: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:104:14: Context: This is the declaration of the getter 'D1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:97:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:112:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:117:16: Error: The type 'int' of the inherited getter 'D1.property2' is not assignable to the type 'String' of the inherited setter 'D2.property2'.
 // abstract class D4
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:11: Context: This is the declaration of the getter 'D1.property2'.
 //   int get property2;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property2'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:110:12: Context: This is the declaration of the setter 'D2.property2'.
 //   void set property2(String i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:102:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:117:16: Error: The type 'String' of the inherited getter 'D1.property3' is not assignable to the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4
 //                ^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:89:14: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:104:14: Context: This is the declaration of the getter 'D1.property3'.
 //   String get property3;
 //              ^^^^^^^^^
-// pkg/front_end/testcases/general/getter_vs_setter_type.dart:97:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:112:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:130:14: Error: The type 'String' of the getter 'property3' is not assignable to the type 'int' of the setter 'property3'.
+//   String get property3 => ''; // error
+//              ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:131:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:142:14: Error: The type 'String' of the getter 'property6' is not assignable to the type 'S' of the setter 'property6'.
+//   String get property6 => ''; // error
+//              ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:143:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(S i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:154:18: Error: The type 'num' of the getter 'property9' is not assignable to the type 'String' of the setter 'property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:155:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(String value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be assigned to a variable of type 'S'.
+//   S get property4 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:136:23: Error: A value of type 'int' can't be assigned to a variable of type 'S'.
+//   S get property5a => 0; // ok
+//                       ^
+//
+// pkg/front_end/testcases/general/getter_vs_setter_type.dart:139:23: Error: A value of type 'int' can't be assigned to a variable of type 'T'.
+//   T get property5b => 0; // ok
+//                       ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -133,10 +173,24 @@
     ;
   abstract get property1() → core::int*;
   abstract set property1(core::int* i) → void;
-  abstract get property2() → core::int*;
-  abstract set property2(core::int* i) → void;
+  abstract get property2a() → core::num*;
+  abstract set property2a(core::int* i) → void;
+  abstract get property2b() → core::int*;
+  abstract set property2b(core::num* i) → void;
   abstract get property3() → core::String*;
   abstract set property3(core::int* i) → void;
+  static get property7() → core::int*
+    return 0;
+  static set property7(core::int* value) → void {}
+  static get property8a() → core::int*
+    return 0;
+  static set property8a(core::num* value) → void {}
+  static get property8b() → core::num*
+    return 0;
+  static set property8b(core::int* value) → void {}
+  static get property9() → core::num*
+    return 0;
+  static set property9(core::String* value) → void {}
   abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
   abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
   abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
@@ -298,4 +352,72 @@
   abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
   abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
 }
+extension Extension<T extends core::num* = core::num*, S extends T* = core::num*> on core::int* {
+  get property1 = self::Extension|get#property1;
+  get property2a = self::Extension|get#property2a;
+  get property2b = self::Extension|get#property2b;
+  get property3 = self::Extension|get#property3;
+  get property4 = self::Extension|get#property4;
+  get property5a = self::Extension|get#property5a;
+  get property5b = self::Extension|get#property5b;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8a = get self::Extension|property8a;
+  static get property8b = get self::Extension|property8b;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2a = self::Extension|set#property2a;
+  set property2b = self::Extension|set#property2b;
+  set property3 = self::Extension|set#property3;
+  set property4 = self::Extension|set#property4;
+  set property5a = self::Extension|set#property5a;
+  set property5b = self::Extension|set#property5b;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8a = set self::Extension|property8a;
+  static set property8b = set self::Extension|property8b;
+  static set property9 = set self::Extension|property9;
+}
+static method Extension|get#property1<T extends core::num* = core::num*, S extends self::Extension|get#property1::T* = core::num*>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#property1<T extends core::num* = core::num*, S extends self::Extension|set#property1::T* = core::num*>(final core::int* #this, core::int* i) → void {}
+static method Extension|get#property2a<T extends core::num* = core::num*, S extends self::Extension|get#property2a::T* = core::num*>(final core::int* #this) → core::num*
+  return 0;
+static method Extension|set#property2a<T extends core::num* = core::num*, S extends self::Extension|set#property2a::T* = core::num*>(final core::int* #this, core::int* i) → void {}
+static method Extension|get#property2b<T extends core::num* = core::num*, S extends self::Extension|get#property2b::T* = core::num*>(final core::int* #this) → core::int*
+  return 0;
+static method Extension|set#property2b<T extends core::num* = core::num*, S extends self::Extension|set#property2b::T* = core::num*>(final core::int* #this, core::num* i) → void {}
+static method Extension|get#property3<T extends core::num* = core::num*, S extends self::Extension|get#property3::T* = core::num*>(final core::int* #this) → core::String*
+  return "";
+static method Extension|set#property3<T extends core::num* = core::num*, S extends self::Extension|set#property3::T* = core::num*>(final core::int* #this, core::int* i) → void {}
+static method Extension|get#property4<T extends core::num* = core::num*, S extends self::Extension|get#property4::T* = core::num*>(final core::int* #this) → self::Extension|get#property4::S*
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/general/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be assigned to a variable of type 'S'.
+  S get property4 => 0; // ok
+                     ^" in 0 as{TypeError} <BottomType>;
+static method Extension|set#property4<T extends core::num* = core::num*, S extends self::Extension|set#property4::T* = core::num*>(final core::int* #this, self::Extension|set#property4::S* i) → void {}
+static method Extension|get#property5a<T extends core::num* = core::num*, S extends self::Extension|get#property5a::T* = core::num*>(final core::int* #this) → self::Extension|get#property5a::S*
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/general/getter_vs_setter_type.dart:136:23: Error: A value of type 'int' can't be assigned to a variable of type 'S'.
+  S get property5a => 0; // ok
+                      ^" in 0 as{TypeError} <BottomType>;
+static method Extension|set#property5a<T extends core::num* = core::num*, S extends self::Extension|set#property5a::T* = core::num*>(final core::int* #this, self::Extension|set#property5a::T* i) → void {}
+static method Extension|get#property5b<T extends core::num* = core::num*, S extends self::Extension|get#property5b::T* = core::num*>(final core::int* #this) → self::Extension|get#property5b::T*
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/general/getter_vs_setter_type.dart:139:23: Error: A value of type 'int' can't be assigned to a variable of type 'T'.
+  T get property5b => 0; // ok
+                      ^" in 0 as{TypeError} <BottomType>;
+static method Extension|set#property5b<T extends core::num* = core::num*, S extends self::Extension|set#property5b::T* = core::num*>(final core::int* #this, self::Extension|set#property5b::S* i) → void {}
+static method Extension|get#property6<T extends core::num* = core::num*, S extends self::Extension|get#property6::T* = core::num*>(final core::int* #this) → core::String*
+  return "";
+static method Extension|set#property6<T extends core::num* = core::num*, S extends self::Extension|set#property6::T* = core::num*>(final core::int* #this, self::Extension|set#property6::S* i) → void {}
+static get Extension|property7() → core::int*
+  return 0;
+static set Extension|property7(core::int* value) → void {}
+static get Extension|property8a() → core::int*
+  return 0;
+static set Extension|property8a(core::num* value) → void {}
+static get Extension|property8b() → core::num*
+  return 0;
+static set Extension|property8b(core::int* value) → void {}
+static get Extension|property9() → core::num*
+  return 0;
+static set Extension|property9(core::String* value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline.expect b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline.expect
index 2018462..47e2d86 100644
--- a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline.expect
+++ b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline.expect
@@ -1,15 +1,24 @@
 abstract class A {
   int get property1;
   void set property1(int i);
-  int get property2;
-  void set property2(int i);
+  num get property2a;
+  void set property2a(int i);
+  int get property2b;
+  void set property2b(num i);
   String get property3;
   void set property3(int i);
   int property4;
   int property5;
   covariant String property6;
+  static int get property7 => 0;
+  static void set property7(int value) {}
+  static int get property8a => 0;
+  static void set property8a(num value) {}
+  static num get property8b => 0;
+  static void set property8b(int value) {}
+  static num get property9 => 0;
+  static void set property9(String value) {}
 }
-
 abstract class B1 {
   int get property1;
   int get property2;
@@ -19,7 +28,6 @@
   final String property6;
   B1(this.property4, this.property5, this.property6);
 }
-
 abstract class B2 implements B1 {
   void set property1(int i);
   void set property2(String i);
@@ -28,7 +36,6 @@
   void set property5(String i);
   void set property6(int i);
 }
-
 abstract class C1 {
   void set property1(int i);
   void set property2(String i);
@@ -37,7 +44,6 @@
   String property5;
   int property6;
 }
-
 abstract class C2 implements C1 {
   int get property1;
   int get property2;
@@ -46,21 +52,18 @@
   int get property5;
   String get property6;
 }
-
 abstract class D1 {
   int get property1;
   int get property2;
   String get property3;
 }
-
 abstract class D2 {
   void set property1(int i);
   void set property2(String i);
   void set property3(int i);
 }
-
 abstract class D3 implements D1, D2 {}
-
 abstract class D4 implements D3 {}
-
+extension Extension<T extends num, S extends T> (){}
+on int (){}
 main() {}
diff --git a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline_modelled.expect
index 22c0c24..e2ee020 100644
--- a/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline_modelled.expect
+++ b/pkg/front_end/testcases/general/getter_vs_setter_type.dart.textual_outline_modelled.expect
@@ -2,11 +2,21 @@
   String get property3;
   covariant String property6;
   int get property1;
-  int get property2;
+  int get property2b;
   int property4;
   int property5;
+  num get property2a;
+  static int get property7 => 0;
+  static int get property8a => 0;
+  static num get property8b => 0;
+  static num get property9 => 0;
+  static void set property7(int value) {}
+  static void set property8a(num value) {}
+  static void set property8b(int value) {}
+  static void set property9(String value) {}
   void set property1(int i);
-  void set property2(int i);
+  void set property2a(int i);
+  void set property2b(num i);
   void set property3(int i);
 }
 
diff --git a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.outline.expect b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.outline.expect
index 2bd2465..bd2765e 100644
--- a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.outline.expect
+++ b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.outline.expect
@@ -1,4 +1,16 @@
 library test;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:28:7: Error: The type 'A' of the getter 'target' is not assignable to the type 'B' of the setter 'target'.
+//  - 'A' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+//  - 'B' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+// A get target => null;
+//       ^^^^^^
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:30:10: Context: This is the declaration of the setter 'target'.
+// void set target(B value) {}
+//          ^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.expect b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.expect
index c956d22..a2976ca 100644
--- a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.expect
+++ b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.expect
@@ -1,4 +1,16 @@
 library test;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:28:7: Error: The type 'A' of the getter 'target' is not assignable to the type 'B' of the setter 'target'.
+//  - 'A' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+//  - 'B' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+// A get target => null;
+//       ^^^^^^
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:30:10: Context: This is the declaration of the setter 'target'.
+// void set target(B value) {}
+//          ^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.transformed.expect b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.transformed.expect
index c956d22..a2976ca 100644
--- a/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/inference_new/static_assign_combiner.dart.strong.transformed.expect
@@ -1,4 +1,16 @@
 library test;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:28:7: Error: The type 'A' of the getter 'target' is not assignable to the type 'B' of the setter 'target'.
+//  - 'A' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+//  - 'B' is from 'pkg/front_end/testcases/inference_new/static_assign_combiner.dart'.
+// A get target => null;
+//       ^^^^^^
+// pkg/front_end/testcases/inference_new/static_assign_combiner.dart:30:10: Context: This is the declaration of the setter 'target'.
+// void set target(B value) {}
+//          ^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart
index aaba82c..1aaaf23 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart
@@ -2,6 +2,15 @@
 // 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.
 
+int get property1 => 0; // ok
+void set property1(int value) {}
+
+int get property2 => 0; // ok
+void set property2(num value) {}
+
+num get property3 => 0; // error
+void set property3(int value) {}
+
 abstract class A {
   int get property1; // ok
   void set property1(int i);
@@ -17,6 +26,15 @@
   int property5 = 0; // ok
 
   covariant num property6 = 0; // ok
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8 => 0; // ok
+  static void set property8(num value) {}
+
+  static num get property9 => 0; // error
+  static void set property9(int value) {}
 }
 
 abstract class B1 {
@@ -99,4 +117,33 @@
 
 abstract class D4 implements D3 /* no need for error on property3 */ {}
 
+extension Extension<T, S extends T> on int {
+  int get property1 => 0; // ok
+  void set property1(int i) {}
+
+  int get property2 => 0; // ok
+  void set property2(num i) {}
+
+  num get property3 => 0; // error
+  void set property3(int i) {}
+
+  S get property4 => 0; // ok
+  void set property4(S i) {}
+
+  S get property5 => 0; // ok
+  void set property5(T i) {}
+
+  T get property6 => 0; // error
+  void set property6(S i) {}
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8 => 0; // ok
+  static void set property8(num value) {}
+
+  static num get property9 => 0; // error
+  static void set property9(int value) {}
+}
+
 main() {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.outline.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.outline.expect
index e7d6448..fb834d9 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.outline.expect
@@ -2,69 +2,104 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:21:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:13:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:43:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:36:18: Error: The type 'num' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:37:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:61:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:27:11: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:45:11: Context: This is the declaration of the getter 'B1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:49:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:67:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:33:13: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:51:13: Context: This is the declaration of the field 'B1.property6'.
 //   final num property6;
 //             ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:71:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:89:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:57:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:75:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   num get property6; // error
 //           ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the overridden method ('property6').
 //   int property6 = 0;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   num get property6; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6 = 0;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:98:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:116:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:100:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:118:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:11:9: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// num get property3 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:127:11: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   num get property3 => 0; // error
+//           ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:128:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:9: Error: The type 'T' of the getter 'property6' is not a subtype of the type 'S' of the setter 'property6'.
+//   T get property6 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:137:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(S i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:145:18: Error: The type 'num' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:146:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -80,6 +115,18 @@
   abstract set property2(core::int i) → void;
   abstract get property3() → core::num;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    ;
+  static set property7(core::int value) → void
+    ;
+  static get property8() → core::int
+    ;
+  static set property8(core::num value) → void
+    ;
+  static get property9() → core::num
+    ;
+  static set property9(core::int value) → void
+    ;
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -143,5 +190,73 @@
   synthetic constructor •() → self::D4
     ;
 }
+extension Extension<T extends core::Object? = dynamic, S extends T% = dynamic> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4 = self::Extension|get#property4;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4 = self::Extension|set#property4;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  ;
+static set property1(core::int value) → void
+  ;
+static get property2() → core::int
+  ;
+static set property2(core::num value) → void
+  ;
+static get property3() → core::num
+  ;
+static set property3(core::int value) → void
+  ;
+static method Extension|get#property1<T extends core::Object? = dynamic, S extends self::Extension|get#property1::T% = dynamic>(final core::int #this) → core::int
+  ;
+static method Extension|set#property1<T extends core::Object? = dynamic, S extends self::Extension|set#property1::T% = dynamic>(final core::int #this, core::int i) → void
+  ;
+static method Extension|get#property2<T extends core::Object? = dynamic, S extends self::Extension|get#property2::T% = dynamic>(final core::int #this) → core::int
+  ;
+static method Extension|set#property2<T extends core::Object? = dynamic, S extends self::Extension|set#property2::T% = dynamic>(final core::int #this, core::num i) → void
+  ;
+static method Extension|get#property3<T extends core::Object? = dynamic, S extends self::Extension|get#property3::T% = dynamic>(final core::int #this) → core::num
+  ;
+static method Extension|set#property3<T extends core::Object? = dynamic, S extends self::Extension|set#property3::T% = dynamic>(final core::int #this, core::int i) → void
+  ;
+static method Extension|get#property4<T extends core::Object? = dynamic, S extends self::Extension|get#property4::T% = dynamic>(final core::int #this) → self::Extension|get#property4::S%
+  ;
+static method Extension|set#property4<T extends core::Object? = dynamic, S extends self::Extension|set#property4::T% = dynamic>(final core::int #this, self::Extension|set#property4::S% i) → void
+  ;
+static method Extension|get#property5<T extends core::Object? = dynamic, S extends self::Extension|get#property5::T% = dynamic>(final core::int #this) → self::Extension|get#property5::S%
+  ;
+static method Extension|set#property5<T extends core::Object? = dynamic, S extends self::Extension|set#property5::T% = dynamic>(final core::int #this, self::Extension|set#property5::T% i) → void
+  ;
+static method Extension|get#property6<T extends core::Object? = dynamic, S extends self::Extension|get#property6::T% = dynamic>(final core::int #this) → self::Extension|get#property6::T%
+  ;
+static method Extension|set#property6<T extends core::Object? = dynamic, S extends self::Extension|set#property6::T% = dynamic>(final core::int #this, self::Extension|set#property6::S% i) → void
+  ;
+static get Extension|property7() → core::int
+  ;
+static set Extension|property7(core::int value) → void
+  ;
+static get Extension|property8() → core::int
+  ;
+static set Extension|property8(core::num value) → void
+  ;
+static get Extension|property9() → core::num
+  ;
+static set Extension|property9(core::int value) → void
+  ;
 static method main() → dynamic
   ;
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.strong.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.strong.expect
index 5c5052b..f346415 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.strong.expect
@@ -2,69 +2,116 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:21:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:13:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:43:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:36:18: Error: The type 'num' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:37:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:61:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:27:11: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:45:11: Context: This is the declaration of the getter 'B1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:49:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:67:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:33:13: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:51:13: Context: This is the declaration of the field 'B1.property6'.
 //   final num property6;
 //             ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:71:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:89:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:57:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:75:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   num get property6; // error
 //           ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the overridden method ('property6').
 //   int property6 = 0;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   num get property6; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6 = 0;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:98:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:116:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:100:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:118:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:11:9: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// num get property3 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:127:11: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   num get property3 => 0; // error
+//           ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:128:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:9: Error: The type 'T' of the getter 'property6' is not a subtype of the type 'S' of the setter 'property6'.
+//   T get property6 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:137:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(S i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:145:18: Error: The type 'num' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:146:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:130:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+//   S get property4 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+//   S get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property6 => 0; // error
+//                      ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +128,15 @@
   abstract set property2(core::int i) → void;
   abstract get property3() → core::num;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::num value) → void {}
+  static get property9() → core::num
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +208,66 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::Object? = dynamic, S extends T% = dynamic> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4 = self::Extension|get#property4;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4 = self::Extension|set#property4;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::num value) → void {}
+static get property3() → core::num
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::Object? = dynamic, S extends self::Extension|get#property1::T% = dynamic>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::Object? = dynamic, S extends self::Extension|set#property1::T% = dynamic>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::Object? = dynamic, S extends self::Extension|get#property2::T% = dynamic>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::Object? = dynamic, S extends self::Extension|set#property2::T% = dynamic>(final core::int #this, core::num i) → void {}
+static method Extension|get#property3<T extends core::Object? = dynamic, S extends self::Extension|get#property3::T% = dynamic>(final core::int #this) → core::num
+  return 0;
+static method Extension|set#property3<T extends core::Object? = dynamic, S extends self::Extension|set#property3::T% = dynamic>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4<T extends core::Object? = dynamic, S extends self::Extension|get#property4::T% = dynamic>(final core::int #this) → self::Extension|get#property4::S%
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:130:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+  S get property4 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4<T extends core::Object? = dynamic, S extends self::Extension|set#property4::T% = dynamic>(final core::int #this, self::Extension|set#property4::S% i) → void {}
+static method Extension|get#property5<T extends core::Object? = dynamic, S extends self::Extension|get#property5::T% = dynamic>(final core::int #this) → self::Extension|get#property5::S%
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+  S get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::Object? = dynamic, S extends self::Extension|set#property5::T% = dynamic>(final core::int #this, self::Extension|set#property5::T% i) → void {}
+static method Extension|get#property6<T extends core::Object? = dynamic, S extends self::Extension|get#property6::T% = dynamic>(final core::int #this) → self::Extension|get#property6::T%
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property6 => 0; // error
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::Object? = dynamic, S extends self::Extension|set#property6::T% = dynamic>(final core::int #this, self::Extension|set#property6::S% i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::num value) → void {}
+static get Extension|property9() → core::num
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline.expect
index bc0af57..806128e 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline.expect
@@ -1,3 +1,9 @@
+int get property1 => 0;
+void set property1(int value) {}
+int get property2 => 0;
+void set property2(num value) {}
+num get property3 => 0;
+void set property3(int value) {}
 abstract class A {
   int get property1;
   void set property1(int i);
@@ -8,8 +14,13 @@
   int property4 = 0;
   int property5 = 0;
   covariant num property6 = 0;
+  static int get property7 => 0;
+  static void set property7(int value) {}
+  static int get property8 => 0;
+  static void set property8(num value) {}
+  static num get property9 => 0;
+  static void set property9(int value) {}
 }
-
 abstract class B1 {
   int get property1;
   int get property2;
@@ -19,7 +30,6 @@
   final num property6;
   B1(this.property4, this.property5, this.property6);
 }
-
 abstract class B2 implements B1 {
   void set property1(int i);
   void set property2(num i);
@@ -28,7 +38,6 @@
   void set property5(num i);
   void set property6(int i);
 }
-
 abstract class C1 {
   void set property1(int i);
   void set property2(num i);
@@ -37,7 +46,6 @@
   num property5 = 0;
   int property6 = 0;
 }
-
 abstract class C2 implements C1 {
   int get property1;
   int get property2;
@@ -46,21 +54,18 @@
   int get property5;
   num get property6;
 }
-
 abstract class D1 {
   int get property1;
   int get property2;
   num get property3;
 }
-
 abstract class D2 {
   void set property1(int i);
   void set property2(num i);
   void set property3(int i);
 }
-
 abstract class D3 implements D1, D2 {}
-
 abstract class D4 implements D3 {}
-
+extension Extension<T, S extends T> (){}
+on int (){}
 main() {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline_modelled.expect
index 43c1a56..feb0a3a 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline_modelled.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.textual_outline_modelled.expect
@@ -5,6 +5,12 @@
   int property4 = 0;
   int property5 = 0;
   num get property3;
+  static int get property7 => 0;
+  static int get property8 => 0;
+  static num get property9 => 0;
+  static void set property7(int value) {}
+  static void set property8(num value) {}
+  static void set property9(int value) {}
   void set property1(int i);
   void set property2(int i);
   void set property3(int i);
@@ -63,4 +69,10 @@
 
 abstract class D4 implements D3 {}
 
+int get property1 => 0;
+int get property2 => 0;
 main() {}
+num get property3 => 0;
+void set property1(int value) {}
+void set property2(num value) {}
+void set property3(int value) {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.weak.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.weak.expect
index 5c5052b..f346415 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart.weak.expect
@@ -2,69 +2,116 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:21:11: Error: The type 'num' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:13:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:43:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:36:18: Error: The type 'num' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:37:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:61:12: Error: The type 'num' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:27:11: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:45:11: Context: This is the declaration of the getter 'B1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:49:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:67:12: Error: The type 'num' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:33:13: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:51:13: Context: This is the declaration of the field 'B1.property6'.
 //   final num property6;
 //             ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:71:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:89:11: Error: The type 'num' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   num get property3; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:57:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:75:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The return type of the method 'C2.property6' is 'num', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   num get property6; // error
 //           ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the overridden method ('property6').
 //   int property6 = 0;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:79:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:97:11: Error: The type 'num' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   num get property6; // error
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:63:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:81:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6 = 0;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:98:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:116:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:100:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:118:16: Error: The type 'num' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:87:11: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:105:11: Context: This is the declaration of the getter 'D1.property3'.
 //   num get property3;
 //           ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:95:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:113:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:11:9: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// num get property3 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:127:11: Error: The type 'num' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   num get property3 => 0; // error
+//           ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:128:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:9: Error: The type 'T' of the getter 'property6' is not a subtype of the type 'S' of the setter 'property6'.
+//   T get property6 => 0; // error
+//         ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:137:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(S i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:145:18: Error: The type 'num' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static num get property9 => 0; // error
+//                  ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:146:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:130:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+//   S get property4 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+//   S get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property6 => 0; // error
+//                      ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +128,15 @@
   abstract set property2(core::int i) → void;
   abstract get property3() → core::num;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::num value) → void {}
+  static get property9() → core::num
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +208,66 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::Object? = dynamic, S extends T% = dynamic> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4 = self::Extension|get#property4;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4 = self::Extension|set#property4;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::num value) → void {}
+static get property3() → core::num
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::Object? = dynamic, S extends self::Extension|get#property1::T% = dynamic>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::Object? = dynamic, S extends self::Extension|set#property1::T% = dynamic>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::Object? = dynamic, S extends self::Extension|get#property2::T% = dynamic>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::Object? = dynamic, S extends self::Extension|set#property2::T% = dynamic>(final core::int #this, core::num i) → void {}
+static method Extension|get#property3<T extends core::Object? = dynamic, S extends self::Extension|get#property3::T% = dynamic>(final core::int #this) → core::num
+  return 0;
+static method Extension|set#property3<T extends core::Object? = dynamic, S extends self::Extension|set#property3::T% = dynamic>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4<T extends core::Object? = dynamic, S extends self::Extension|get#property4::T% = dynamic>(final core::int #this) → self::Extension|get#property4::S%
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:130:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+  S get property4 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4<T extends core::Object? = dynamic, S extends self::Extension|set#property4::T% = dynamic>(final core::int #this, self::Extension|set#property4::S% i) → void {}
+static method Extension|get#property5<T extends core::Object? = dynamic, S extends self::Extension|get#property5::T% = dynamic>(final core::int #this) → self::Extension|get#property5::S%
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:133:22: Error: A value of type 'int' can't be returned from a function with return type 'S'.
+  S get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::Object? = dynamic, S extends self::Extension|set#property5::T% = dynamic>(final core::int #this, self::Extension|set#property5::T% i) → void {}
+static method Extension|get#property6<T extends core::Object? = dynamic, S extends self::Extension|get#property6::T% = dynamic>(final core::int #this) → self::Extension|get#property6::T%
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type.dart:136:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property6 => 0; // error
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::Object? = dynamic, S extends self::Extension|set#property6::T% = dynamic>(final core::int #this, self::Extension|set#property6::S% i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::num value) → void {}
+static get Extension|property9() → core::num
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart
index 364f0c6..2156307 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart
@@ -2,17 +2,23 @@
 // 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.
 
+int get property1 => 0; // ok
+void set property1(int value) {}
+
+int get property2 => 0; // ok
+void set property2(int? value) {}
+
+int? get property3 => 0; // error
+void set property3(int value) {}
+
 abstract class A {
   int get property1; // ok
-
   void set property1(int i);
 
   int get property2; // ok
-
   void set property2(int? i);
 
   int? get property3; // error
-
   void set property3(int i);
 
   int property4; // ok
@@ -22,6 +28,15 @@
   covariant int property6; // ok
 
   A(this.property4, this.property5, this.property6);
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8 => 0; // ok
+  static void set property8(int? value) {}
+
+  static int? get property9 => 0; // error
+  static void set property9(int value) {}
 }
 
 abstract class B1 {
@@ -106,4 +121,36 @@
 
 abstract class D4 implements D3 /* no need for error on property3 */ {}
 
+extension Extension<T extends num> on int {
+  int get property1 => 0; // ok
+  void set property1(int i) {}
+
+  int get property2 => 0; // ok
+  void set property2(int? i) {}
+
+  int? get property3 => 0; // error
+  void set property3(int i) {}
+
+  T get property4a => 0; // ok
+  void set property4a(T i) {}
+
+  T? get property4b => 0; // ok
+  void set property4b(T? i) {}
+
+  T get property5 => 0; // ok
+  void set property5(T? i) {}
+
+  T? get property6 => 0; // error
+  void set property6(T i) {}
+
+  static int get property7 => 0; // ok
+  static void set property7(int value) {}
+
+  static int get property8 => 0; // ok
+  static void set property8(int? value) {}
+
+  static int? get property9 => 0; // error
+  static void set property9(int value) {}
+}
+
 main() {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.outline.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.outline.expect
index 30e3ae5..763d5e7 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.outline.expect
@@ -2,69 +2,104 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:14:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:21:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:48:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:19: Error: The type 'int?' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:39:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:63:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:32:12: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:47:12: Context: This is the declaration of the getter 'B1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:54:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:69:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:14: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:53:14: Context: This is the declaration of the field 'B1.property6'.
 //   final int? property6;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:78:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:93:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:62:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:77:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   int? get property6; // error
 //            ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   int? get property6; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:105:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:120:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:107:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:122:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:11:10: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// int? get property3 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:131:12: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   int? get property3 => 0; // error
+//            ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:132:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:10: Error: The type 'T?' of the getter 'property6' is not a subtype of the type 'T' of the setter 'property6'.
+//   T? get property6 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:144:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(T i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:152:19: Error: The type 'int?' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:153:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -80,6 +115,18 @@
   abstract set property2(core::int? i) → void;
   abstract get property3() → core::int?;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    ;
+  static set property7(core::int value) → void
+    ;
+  static get property8() → core::int
+    ;
+  static set property8(core::int? value) → void
+    ;
+  static get property9() → core::int?
+    ;
+  static set property9(core::int value) → void
+    ;
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -143,5 +190,79 @@
   synthetic constructor •() → self::D4
     ;
 }
+extension Extension<T extends core::num = core::num> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4a = self::Extension|get#property4a;
+  get property4b = self::Extension|get#property4b;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4a = self::Extension|set#property4a;
+  set property4b = self::Extension|set#property4b;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  ;
+static set property1(core::int value) → void
+  ;
+static get property2() → core::int
+  ;
+static set property2(core::int? value) → void
+  ;
+static get property3() → core::int?
+  ;
+static set property3(core::int value) → void
+  ;
+static method Extension|get#property1<T extends core::num = core::num>(final core::int #this) → core::int
+  ;
+static method Extension|set#property1<T extends core::num = core::num>(final core::int #this, core::int i) → void
+  ;
+static method Extension|get#property2<T extends core::num = core::num>(final core::int #this) → core::int
+  ;
+static method Extension|set#property2<T extends core::num = core::num>(final core::int #this, core::int? i) → void
+  ;
+static method Extension|get#property3<T extends core::num = core::num>(final core::int #this) → core::int?
+  ;
+static method Extension|set#property3<T extends core::num = core::num>(final core::int #this, core::int i) → void
+  ;
+static method Extension|get#property4a<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4a::T
+  ;
+static method Extension|set#property4a<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4a::T i) → void
+  ;
+static method Extension|get#property4b<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4b::T?
+  ;
+static method Extension|set#property4b<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4b::T? i) → void
+  ;
+static method Extension|get#property5<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property5::T
+  ;
+static method Extension|set#property5<T extends core::num = core::num>(final core::int #this, self::Extension|set#property5::T? i) → void
+  ;
+static method Extension|get#property6<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property6::T?
+  ;
+static method Extension|set#property6<T extends core::num = core::num>(final core::int #this, self::Extension|set#property6::T i) → void
+  ;
+static get Extension|property7() → core::int
+  ;
+static set Extension|property7(core::int value) → void
+  ;
+static get Extension|property8() → core::int
+  ;
+static set Extension|property8(core::int? value) → void
+  ;
+static get Extension|property9() → core::int?
+  ;
+static set Extension|property9(core::int value) → void
+  ;
 static method main() → dynamic
   ;
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.expect
index 89fd1f6..40207f8 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.expect
@@ -2,69 +2,120 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:14:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:21:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:48:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:19: Error: The type 'int?' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:39:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:63:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:32:12: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:47:12: Context: This is the declaration of the getter 'B1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:54:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:69:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:14: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:53:14: Context: This is the declaration of the field 'B1.property6'.
 //   final int? property6;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:78:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:93:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:62:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:77:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   int? get property6; // error
 //            ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   int? get property6; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:105:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:120:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:107:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:122:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:11:10: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// int? get property3 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:131:12: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   int? get property3 => 0; // error
+//            ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:132:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:10: Error: The type 'T?' of the getter 'property6' is not a subtype of the type 'T' of the setter 'property6'.
+//   T? get property6 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:144:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(T i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:152:19: Error: The type 'int?' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:153:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property4a => 0; // ok
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property4b => 0; // ok
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property6 => 0; // error
+//                       ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +132,15 @@
   abstract set property2(core::int? i) → void;
   abstract get property3() → core::int?;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::int? value) → void {}
+  static get property9() → core::int?
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +212,73 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::num = core::num> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4a = self::Extension|get#property4a;
+  get property4b = self::Extension|get#property4b;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4a = self::Extension|set#property4a;
+  set property4b = self::Extension|set#property4b;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::int? value) → void {}
+static get property3() → core::int?
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::num = core::num>(final core::int #this, core::int? i) → void {}
+static method Extension|get#property3<T extends core::num = core::num>(final core::int #this) → core::int?
+  return 0;
+static method Extension|set#property3<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4a<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4a::T
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property4a => 0; // ok
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4a<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4a::T i) → void {}
+static method Extension|get#property4b<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4b::T?
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property4b => 0; // ok
+                       ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4b<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4b::T? i) → void {}
+static method Extension|get#property5<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property5::T
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::num = core::num>(final core::int #this, self::Extension|set#property5::T? i) → void {}
+static method Extension|get#property6<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property6::T?
+  return let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property6 => 0; // error
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::num = core::num>(final core::int #this, self::Extension|set#property6::T i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::int? value) → void {}
+static get Extension|property9() → core::int?
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.transformed.expect
index 89fd1f6..40207f8 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.strong.transformed.expect
@@ -2,69 +2,120 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:14:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:21:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:48:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:19: Error: The type 'int?' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:39:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:63:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:32:12: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:47:12: Context: This is the declaration of the getter 'B1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:54:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:69:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:14: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:53:14: Context: This is the declaration of the field 'B1.property6'.
 //   final int? property6;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:78:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:93:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:62:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:77:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   int? get property6; // error
 //            ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   int? get property6; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:105:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:120:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:107:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:122:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:11:10: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// int? get property3 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:131:12: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   int? get property3 => 0; // error
+//            ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:132:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:10: Error: The type 'T?' of the getter 'property6' is not a subtype of the type 'T' of the setter 'property6'.
+//   T? get property6 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:144:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(T i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:152:19: Error: The type 'int?' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:153:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property4a => 0; // ok
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property4b => 0; // ok
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property6 => 0; // error
+//                       ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +132,15 @@
   abstract set property2(core::int? i) → void;
   abstract get property3() → core::int?;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::int? value) → void {}
+  static get property9() → core::int?
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +212,73 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::num = core::num> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4a = self::Extension|get#property4a;
+  get property4b = self::Extension|get#property4b;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4a = self::Extension|set#property4a;
+  set property4b = self::Extension|set#property4b;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::int? value) → void {}
+static get property3() → core::int?
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::num = core::num>(final core::int #this, core::int? i) → void {}
+static method Extension|get#property3<T extends core::num = core::num>(final core::int #this) → core::int?
+  return 0;
+static method Extension|set#property3<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4a<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4a::T
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property4a => 0; // ok
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4a<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4a::T i) → void {}
+static method Extension|get#property4b<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4b::T?
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property4b => 0; // ok
+                       ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4b<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4b::T? i) → void {}
+static method Extension|get#property5<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property5::T
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::num = core::num>(final core::int #this, self::Extension|set#property5::T? i) → void {}
+static method Extension|get#property6<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property6::T?
+  return let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property6 => 0; // error
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::num = core::num>(final core::int #this, self::Extension|set#property6::T i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::int? value) → void {}
+static get Extension|property9() → core::int?
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline.expect
index b6be33e..1bfebe7 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline.expect
@@ -1,3 +1,9 @@
+int get property1 => 0;
+void set property1(int value) {}
+int get property2 => 0;
+void set property2(int? value) {}
+int? get property3 => 0;
+void set property3(int value) {}
 abstract class A {
   int get property1;
   void set property1(int i);
@@ -9,8 +15,13 @@
   int? property5;
   covariant int property6;
   A(this.property4, this.property5, this.property6);
+  static int get property7 => 0;
+  static void set property7(int value) {}
+  static int get property8 => 0;
+  static void set property8(int? value) {}
+  static int? get property9 => 0;
+  static void set property9(int value) {}
 }
-
 abstract class B1 {
   int get property1;
   int get property2;
@@ -20,7 +31,6 @@
   final int? property6;
   B1(this.property4, this.property5, this.property6);
 }
-
 abstract class B2 implements B1 {
   void set property1(int i);
   void set property2(int? i);
@@ -29,7 +39,6 @@
   void set property5(int? i);
   void set property6(int i);
 }
-
 abstract class C1 {
   void set property1(int i);
   void set property2(int? i);
@@ -39,7 +48,6 @@
   int property6;
   C1(this.property4, this.property5, this.property6);
 }
-
 abstract class C2 implements C1 {
   int get property1;
   int get property2;
@@ -48,21 +56,18 @@
   int get property5;
   int? get property6;
 }
-
 abstract class D1 {
   int get property1;
   int get property2;
   int? get property3;
 }
-
 abstract class D2 {
   void set property1(int i);
   void set property2(int? i);
   void set property3(int i);
 }
-
 abstract class D3 implements D1, D2 {}
-
 abstract class D4 implements D3 {}
-
+extension Extension<T extends num> (){}
+on int (){}
 main() {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline_modelled.expect
index a071d28..30cbfa9 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline_modelled.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.textual_outline_modelled.expect
@@ -6,6 +6,12 @@
   int get property1;
   int get property2;
   int property4;
+  static int? get property9 => 0;
+  static int get property7 => 0;
+  static int get property8 => 0;
+  static void set property7(int value) {}
+  static void set property8(int? value) {}
+  static void set property9(int value) {}
   void set property1(int i);
   void set property2(int? i);
   void set property3(int i);
@@ -65,4 +71,10 @@
 
 abstract class D4 implements D3 {}
 
+int? get property3 => 0;
+int get property1 => 0;
+int get property2 => 0;
 main() {}
+void set property1(int value) {}
+void set property2(int? value) {}
+void set property3(int value) {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.expect
index 89fd1f6..40207f8 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.expect
@@ -2,69 +2,120 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:14:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:21:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:48:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:19: Error: The type 'int?' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:39:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:63:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:32:12: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:47:12: Context: This is the declaration of the getter 'B1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:54:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:69:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:14: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:53:14: Context: This is the declaration of the field 'B1.property6'.
 //   final int? property6;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:78:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:93:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:62:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:77:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   int? get property6; // error
 //            ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   int? get property6; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:105:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:120:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:107:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:122:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:11:10: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// int? get property3 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:131:12: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   int? get property3 => 0; // error
+//            ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:132:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:10: Error: The type 'T?' of the getter 'property6' is not a subtype of the type 'T' of the setter 'property6'.
+//   T? get property6 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:144:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(T i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:152:19: Error: The type 'int?' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:153:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property4a => 0; // ok
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property4b => 0; // ok
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property6 => 0; // error
+//                       ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +132,15 @@
   abstract set property2(core::int? i) → void;
   abstract get property3() → core::int?;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::int? value) → void {}
+  static get property9() → core::int?
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +212,73 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::num = core::num> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4a = self::Extension|get#property4a;
+  get property4b = self::Extension|get#property4b;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4a = self::Extension|set#property4a;
+  set property4b = self::Extension|set#property4b;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::int? value) → void {}
+static get property3() → core::int?
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::num = core::num>(final core::int #this, core::int? i) → void {}
+static method Extension|get#property3<T extends core::num = core::num>(final core::int #this) → core::int?
+  return 0;
+static method Extension|set#property3<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4a<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4a::T
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property4a => 0; // ok
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4a<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4a::T i) → void {}
+static method Extension|get#property4b<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4b::T?
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property4b => 0; // ok
+                       ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4b<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4b::T? i) → void {}
+static method Extension|get#property5<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property5::T
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::num = core::num>(final core::int #this, self::Extension|set#property5::T? i) → void {}
+static method Extension|get#property6<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property6::T?
+  return let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property6 => 0; // error
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::num = core::num>(final core::int #this, self::Extension|set#property6::T i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::int? value) → void {}
+static get Extension|property9() → core::int?
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.transformed.expect
index 89fd1f6..40207f8 100644
--- a/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart.weak.transformed.expect
@@ -2,69 +2,120 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:14:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:21:12: Error: The type 'int?' of the getter 'A.property3' is not a subtype of the type 'int' of the setter 'A.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:16:12: Context: This is the declaration of the setter 'A.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:22:12: Context: This is the declaration of the setter 'A.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:48:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:19: Error: The type 'int?' of the getter 'A.property9' is not a subtype of the type 'int' of the setter 'A.property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:39:19: Context: This is the declaration of the setter 'A.property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:63:12: Error: The type 'int?' of the inherited getter 'B1.property3' is not a subtype of the type 'int' of the setter 'B2.property3'.
 //   void set property3(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:32:12: Context: This is the declaration of the getter 'B1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:47:12: Context: This is the declaration of the getter 'B1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:54:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:69:12: Error: The type 'int?' of the inherited field 'B1.property6' is not a subtype of the type 'int' of the setter 'B2.property6'.
 //   void set property6(int i); // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:38:14: Context: This is the declaration of the field 'B1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:53:14: Context: This is the declaration of the field 'B1.property6'.
 //   final int? property6;
 //              ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:78:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:93:12: Error: The type 'int?' of the getter 'C2.property3' is not a subtype of the type 'int' of the inherited setter 'C1.property3'.
 //   int? get property3; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:62:12: Context: This is the declaration of the setter 'C1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:77:12: Context: This is the declaration of the setter 'C1.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The return type of the method 'C2.property6' is 'int?', which does not match the return type, 'int', of the overridden method, 'C1.property6'.
 // Change to a subtype of 'int'.
 //   int? get property6; // error
 //            ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the overridden method ('property6').
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the overridden method ('property6').
 //   int property6;
 //       ^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:86:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:101:12: Error: The type 'int?' of the getter 'C2.property6' is not a subtype of the type 'int' of the inherited setter 'C1.property6'.
 //   int? get property6; // error
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:68:7: Context: This is the declaration of the setter 'C1.property6'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:83:7: Context: This is the declaration of the setter 'C1.property6'.
 //   int property6;
 //       ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:105:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:120:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D3 implements D1, D2 /* error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:107:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:122:16: Error: The type 'int?' of the inherited getter 'D1.property3' is not a subtype of the type 'int' of the inherited setter 'D2.property3'.
 // abstract class D4 implements D3 /* no need for error on property3 */ {}
 //                ^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:94:12: Context: This is the declaration of the getter 'D1.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:109:12: Context: This is the declaration of the getter 'D1.property3'.
 //   int? get property3;
 //            ^^^^^^^^^
-// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:102:12: Context: This is the declaration of the setter 'D2.property3'.
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:117:12: Context: This is the declaration of the setter 'D2.property3'.
 //   void set property3(int i);
 //            ^^^^^^^^^
 //
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:11:10: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+// int? get property3 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:12:10: Context: This is the declaration of the setter 'property3'.
+// void set property3(int value) {}
+//          ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:131:12: Error: The type 'int?' of the getter 'property3' is not a subtype of the type 'int' of the setter 'property3'.
+//   int? get property3 => 0; // error
+//            ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:132:12: Context: This is the declaration of the setter 'property3'.
+//   void set property3(int i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:10: Error: The type 'T?' of the getter 'property6' is not a subtype of the type 'T' of the setter 'property6'.
+//   T? get property6 => 0; // error
+//          ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:144:12: Context: This is the declaration of the setter 'property6'.
+//   void set property6(T i) {}
+//            ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:152:19: Error: The type 'int?' of the getter 'property9' is not a subtype of the type 'int' of the setter 'property9'.
+//   static int? get property9 => 0; // error
+//                   ^^^^^^^^^
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:153:19: Context: This is the declaration of the setter 'property9'.
+//   static void set property9(int value) {}
+//                   ^^^^^^^^^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property4a => 0; // ok
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property4b => 0; // ok
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+//   T get property5 => 0; // ok
+//                      ^
+//
+// pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+//   T? get property6 => 0; // error
+//                       ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -81,6 +132,15 @@
   abstract set property2(core::int? i) → void;
   abstract get property3() → core::int?;
   abstract set property3(core::int i) → void;
+  static get property7() → core::int
+    return 0;
+  static set property7(core::int value) → void {}
+  static get property8() → core::int
+    return 0;
+  static set property8(core::int? value) → void {}
+  static get property9() → core::int?
+    return 0;
+  static set property9(core::int value) → void {}
 }
 abstract class B1 extends core::Object {
   final field core::int property4;
@@ -152,4 +212,73 @@
     : super core::Object::•()
     ;
 }
+extension Extension<T extends core::num = core::num> on core::int {
+  get property1 = self::Extension|get#property1;
+  get property2 = self::Extension|get#property2;
+  get property3 = self::Extension|get#property3;
+  get property4a = self::Extension|get#property4a;
+  get property4b = self::Extension|get#property4b;
+  get property5 = self::Extension|get#property5;
+  get property6 = self::Extension|get#property6;
+  static get property7 = get self::Extension|property7;
+  static get property8 = get self::Extension|property8;
+  static get property9 = get self::Extension|property9;
+  set property1 = self::Extension|set#property1;
+  set property2 = self::Extension|set#property2;
+  set property3 = self::Extension|set#property3;
+  set property4a = self::Extension|set#property4a;
+  set property4b = self::Extension|set#property4b;
+  set property5 = self::Extension|set#property5;
+  set property6 = self::Extension|set#property6;
+  static set property7 = set self::Extension|property7;
+  static set property8 = set self::Extension|property8;
+  static set property9 = set self::Extension|property9;
+}
+static get property1() → core::int
+  return 0;
+static set property1(core::int value) → void {}
+static get property2() → core::int
+  return 0;
+static set property2(core::int? value) → void {}
+static get property3() → core::int?
+  return 0;
+static set property3(core::int value) → void {}
+static method Extension|get#property1<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property1<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property2<T extends core::num = core::num>(final core::int #this) → core::int
+  return 0;
+static method Extension|set#property2<T extends core::num = core::num>(final core::int #this, core::int? i) → void {}
+static method Extension|get#property3<T extends core::num = core::num>(final core::int #this) → core::int?
+  return 0;
+static method Extension|set#property3<T extends core::num = core::num>(final core::int #this, core::int i) → void {}
+static method Extension|get#property4a<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4a::T
+  return let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:134:23: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property4a => 0; // ok
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4a<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4a::T i) → void {}
+static method Extension|get#property4b<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property4b::T?
+  return let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:137:24: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property4b => 0; // ok
+                       ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property4b<T extends core::num = core::num>(final core::int #this, self::Extension|set#property4b::T? i) → void {}
+static method Extension|get#property5<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property5::T
+  return let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:140:22: Error: A value of type 'int' can't be returned from a function with return type 'T'.
+  T get property5 => 0; // ok
+                     ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property5<T extends core::num = core::num>(final core::int #this, self::Extension|set#property5::T? i) → void {}
+static method Extension|get#property6<T extends core::num = core::num>(final core::int #this) → self::Extension|get#property6::T?
+  return let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/getter_vs_setter_type_nnbd.dart:143:23: Error: A value of type 'int' can't be returned from a function with return type 'T?'.
+  T? get property6 => 0; // error
+                      ^" in 0 as{TypeError,ForNonNullableByDefault} <BottomType>;
+static method Extension|set#property6<T extends core::num = core::num>(final core::int #this, self::Extension|set#property6::T i) → void {}
+static get Extension|property7() → core::int
+  return 0;
+static set Extension|property7(core::int value) → void {}
+static get Extension|property8() → core::int
+  return 0;
+static set Extension|property8(core::int? value) → void {}
+static get Extension|property9() → core::int?
+  return 0;
+static set Extension|property9(core::int value) → void {}
 static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/textual_outline.status b/pkg/front_end/testcases/textual_outline.status
index b53cc5e..17eae7c 100644
--- a/pkg/front_end/testcases/textual_outline.status
+++ b/pkg/front_end/testcases/textual_outline.status
@@ -41,6 +41,7 @@
 extensions/extension_call: FormatterCrash
 extensions/extension_constructor: FormatterCrash
 extensions/extension_field_with_type_parameter_usage: FormatterCrash
+extensions/extension_member_conflict: FormatterCrash
 extensions/extension_methods: FormatterCrash
 extensions/extension_setter: FormatterCrash
 extensions/extension_setter_error: FormatterCrash
@@ -108,6 +109,7 @@
 general/error_recovery/issue_39230.crash: FormatterCrash
 general/error_recovery/issue_39958_01: FormatterCrash
 general/function_type_default_value: FormatterCrash
+general/getter_vs_setter_type: FormatterCrash
 general/incomplete_field_formal_parameter: FormatterCrash
 general/invalid_operator2: FormatterCrash
 general/invalid_operator: FormatterCrash
@@ -171,7 +173,9 @@
 nnbd/external_field_errors: FormatterCrash
 nnbd/external_fields: FormatterCrash
 nnbd/forbidden_supers: FormatterCrash
+nnbd/getter_vs_setter_type: FormatterCrash
 nnbd/getter_vs_setter_type_late: FormatterCrash
+nnbd/getter_vs_setter_type_nnbd: FormatterCrash
 nnbd/infer_if_null: FormatterCrash
 nnbd/inheritance_from_opt_in: FormatterCrash
 nnbd/issue40805: FormatterCrash
diff --git a/runtime/platform/utils.h b/runtime/platform/utils.h
index 57bb31a..baa4ff4 100644
--- a/runtime/platform/utils.h
+++ b/runtime/platform/utils.h
@@ -387,29 +387,6 @@
     return ((mask >> position) & 1) != 0;
   }
 
-  // Decode integer in SLEB128 format from |data| and update |byte_index|.
-  template <typename ValueType>
-  static ValueType DecodeSLEB128(const uint8_t* data,
-                                 const intptr_t data_length,
-                                 intptr_t* byte_index) {
-    using Unsigned = typename std::make_unsigned<ValueType>::type;
-    ASSERT(*byte_index < data_length);
-    uword shift = 0;
-    Unsigned value = 0;
-    uint8_t part = 0;
-    do {
-      part = data[(*byte_index)++];
-      value |= static_cast<Unsigned>(part & 0x7f) << shift;
-      shift += 7;
-    } while ((part & 0x80) != 0);
-
-    if ((shift < (sizeof(ValueType) * CHAR_BIT)) && ((part & 0x40) != 0)) {
-      const Unsigned kMax = std::numeric_limits<Unsigned>::max();
-      value |= static_cast<Unsigned>(kMax << shift);
-    }
-    return static_cast<ValueType>(value);
-  }
-
   static char* StrError(int err, char* buffer, size_t bufsize);
 
   // Not all platforms support strndup.
diff --git a/runtime/vm/bitmap.cc b/runtime/vm/bitmap.cc
index d5e25dd..334c46b 100644
--- a/runtime/vm/bitmap.cc
+++ b/runtime/vm/bitmap.cc
@@ -77,7 +77,7 @@
   }
 }
 
-void BitmapBuilder::AppendAsBytesTo(GrowableArray<uint8_t>* bytes) const {
+void BitmapBuilder::AppendAsBytesTo(BaseWriteStream* stream) const {
   // Early return if there are no bits in the payload to copy.
   if (Length() == 0) return;
 
@@ -94,19 +94,20 @@
     payload_size = total_size;
     extra_size = 0;
   }
+#if defined(DEBUG)
+  // Make sure any bits in the payload beyond the bit length if we're not
+  // appending trailing zeroes are cleared to ensure deterministic snapshots.
+  if (extra_size == 0 && Length() % kBitsPerByte != 0) {
+    const int8_t mask = (1 << (Length() % kBitsPerByte)) - 1;
+    ASSERT_EQUAL(data_[payload_size - 1], (data_[payload_size - 1] & mask));
+  }
+#endif
   for (intptr_t i = 0; i < payload_size; i++) {
-    bytes->Add(data_[i]);
+    stream->WriteByte(data_[i]);
   }
   for (intptr_t i = 0; i < extra_size; i++) {
-    bytes->Add(0U);
+    stream->WriteByte(0U);
   }
-  // Make sure any bits in the payload beyond the bit length are cleared to
-  // ensure deterministic snapshots.
-#if defined(DEBUG)
-  if (Length() % kBitsPerByte == 0) return;
-  const int8_t mask = (1 << (Length() % kBitsPerByte)) - 1;
-  ASSERT(bytes->Last() == (bytes->Last() & mask));
-#endif
 }
 
 bool BitmapBuilder::GetBit(intptr_t bit_offset) const {
diff --git a/runtime/vm/bitmap.h b/runtime/vm/bitmap.h
index 878a834..ed08009 100644
--- a/runtime/vm/bitmap.h
+++ b/runtime/vm/bitmap.h
@@ -6,7 +6,7 @@
 #define RUNTIME_VM_BITMAP_H_
 
 #include "vm/allocation.h"
-#include "vm/growable_array.h"
+#include "vm/datastream.h"
 #include "vm/thread_state.h"
 #include "vm/zone.h"
 
@@ -44,7 +44,7 @@
   void SetRange(intptr_t min, intptr_t max, bool value);
 
   void Print() const;
-  void AppendAsBytesTo(GrowableArray<uint8_t>* bytes) const;
+  void AppendAsBytesTo(BaseWriteStream* stream) const;
 
  private:
   static const intptr_t kInitialSizeInBytes = 16;
diff --git a/runtime/vm/bitmap_test.cc b/runtime/vm/bitmap_test.cc
index 2c7f3d9..c3cd203 100644
--- a/runtime/vm/bitmap_test.cc
+++ b/runtime/vm/bitmap_test.cc
@@ -16,8 +16,8 @@
 static const uint32_t kTestPcOffset = 0x4;
 static const intptr_t kTestSpillSlotBitCount = 0;
 
-static CompressedStackMapsPtr MapsFromBuilder(BitmapBuilder* bmap) {
-  CompressedStackMapsBuilder builder;
+static CompressedStackMapsPtr MapsFromBuilder(Zone* zone, BitmapBuilder* bmap) {
+  CompressedStackMapsBuilder builder(zone);
   builder.AddEntry(kTestPcOffset, bmap, kTestSpillSlotBitCount);
   return builder.Finalize();
 }
@@ -51,8 +51,9 @@
   }
 
   // Create a CompressedStackMaps object and verify its contents.
-  const auto& maps1 = CompressedStackMaps::Handle(MapsFromBuilder(builder1));
-  CompressedStackMapsIterator it1(maps1);
+  const auto& maps1 = CompressedStackMaps::Handle(
+      thread->zone(), MapsFromBuilder(thread->zone(), builder1));
+  CompressedStackMaps::Iterator it1(thread, maps1);
   EXPECT(it1.MoveNext());
 
   EXPECT_EQ(kTestPcOffset, it1.pc_offset());
@@ -83,8 +84,9 @@
     EXPECT(!builder1->Get(i));
   }
 
-  const auto& maps2 = CompressedStackMaps::Handle(MapsFromBuilder(builder1));
-  CompressedStackMapsIterator it2(maps2);
+  const auto& maps2 = CompressedStackMaps::Handle(
+      thread->zone(), MapsFromBuilder(thread->zone(), builder1));
+  CompressedStackMaps::Iterator it2(thread, maps2);
   EXPECT(it2.MoveNext());
 
   EXPECT_EQ(kTestPcOffset, it2.pc_offset());
diff --git a/runtime/vm/code_descriptors.cc b/runtime/vm/code_descriptors.cc
index 2dc5584..edce815 100644
--- a/runtime/vm/code_descriptors.cc
+++ b/runtime/vm/code_descriptors.cc
@@ -35,14 +35,13 @@
         PcDescriptorsLayout::KindAndMetadata::Encode(kind, try_index,
                                                      yield_index);
 
-    PcDescriptors::EncodeInteger(&encoded_data_, kind_and_metadata);
-    PcDescriptors::EncodeInteger(&encoded_data_, pc_offset - prev_pc_offset);
+    encoded_data_.WriteSLEB128(kind_and_metadata);
+    encoded_data_.WriteSLEB128(pc_offset - prev_pc_offset);
     prev_pc_offset = pc_offset;
 
     if (!FLAG_precompiled_mode) {
-      PcDescriptors::EncodeInteger(&encoded_data_, deopt_id - prev_deopt_id);
-      PcDescriptors::EncodeInteger(&encoded_data_,
-                                   token_pos.value() - prev_token_pos);
+      encoded_data_.WriteSLEB128(deopt_id - prev_deopt_id);
+      encoded_data_.WriteSLEB128(token_pos.value() - prev_token_pos);
       prev_deopt_id = deopt_id;
       prev_token_pos = token_pos.value();
     }
@@ -50,22 +49,11 @@
 }
 
 PcDescriptorsPtr DescriptorList::FinalizePcDescriptors(uword entry_point) {
-  if (encoded_data_.length() == 0) {
+  if (encoded_data_.bytes_written() == 0) {
     return Object::empty_descriptors().raw();
   }
-  return PcDescriptors::New(&encoded_data_);
-}
-
-// Encode unsigned integer |value| in LEB128 format and store into |data|.
-void CompressedStackMapsBuilder::EncodeLEB128(GrowableArray<uint8_t>* data,
-                                              uintptr_t value) {
-  while (true) {
-    uint8_t part = value & 0x7f;
-    value >>= 7;
-    if (value != 0) part |= 0x80;
-    data->Add(part);
-    if (value == 0) break;
-  }
+  return PcDescriptors::New(encoded_data_.buffer(),
+                            encoded_data_.bytes_written());
 }
 
 void CompressedStackMapsBuilder::AddEntry(intptr_t pc_offset,
@@ -74,179 +62,22 @@
   ASSERT(bitmap != nullptr);
   ASSERT(pc_offset > last_pc_offset_);
   ASSERT(spill_slot_bit_count >= 0 && spill_slot_bit_count <= bitmap->Length());
-  auto const pc_delta = pc_offset - last_pc_offset_;
-  auto const non_spill_slot_bit_count = bitmap->Length() - spill_slot_bit_count;
-  EncodeLEB128(&encoded_bytes_, pc_delta);
-  EncodeLEB128(&encoded_bytes_, spill_slot_bit_count);
-  EncodeLEB128(&encoded_bytes_, non_spill_slot_bit_count);
+  const uword pc_delta = pc_offset - last_pc_offset_;
+  const uword non_spill_slot_bit_count =
+      bitmap->Length() - spill_slot_bit_count;
+  encoded_bytes_.WriteLEB128(pc_delta);
+  encoded_bytes_.WriteLEB128(spill_slot_bit_count);
+  encoded_bytes_.WriteLEB128(non_spill_slot_bit_count);
   bitmap->AppendAsBytesTo(&encoded_bytes_);
   last_pc_offset_ = pc_offset;
 }
 
 CompressedStackMapsPtr CompressedStackMapsBuilder::Finalize() const {
-  if (encoded_bytes_.length() == 0) return CompressedStackMaps::null();
-  return CompressedStackMaps::NewInlined(encoded_bytes_);
-}
-
-CompressedStackMapsIterator::CompressedStackMapsIterator(
-    const CompressedStackMaps& maps,
-    const CompressedStackMaps& global_table)
-    : maps_(maps),
-      bits_container_(maps_.UsesGlobalTable() ? global_table : maps_) {
-  ASSERT(!maps_.IsGlobalTable());
-  ASSERT(!maps_.UsesGlobalTable() || bits_container_.IsGlobalTable());
-}
-
-CompressedStackMapsIterator::CompressedStackMapsIterator(
-    const CompressedStackMaps& maps)
-    : CompressedStackMapsIterator(
-          maps,
-          // Only look up the global table if the map will end up using it.
-          maps.UsesGlobalTable() ? CompressedStackMaps::Handle(
-                                       Thread::Current()
-                                           ->isolate()
-                                           ->object_store()
-                                           ->canonicalized_stack_map_entries())
-                                 : Object::null_compressed_stack_maps()) {}
-
-CompressedStackMapsIterator::CompressedStackMapsIterator(
-    const CompressedStackMapsIterator& it)
-    : maps_(it.maps_),
-      bits_container_(it.bits_container_),
-      next_offset_(it.next_offset_),
-      current_pc_offset_(it.current_pc_offset_),
-      current_global_table_offset_(it.current_global_table_offset_),
-      current_spill_slot_bit_count_(it.current_spill_slot_bit_count_),
-      current_non_spill_slot_bit_count_(it.current_spill_slot_bit_count_),
-      current_bits_offset_(it.current_bits_offset_) {}
-
-// Decode unsigned integer in LEB128 format from the payload of |maps| and
-// update |byte_index|.
-uintptr_t CompressedStackMapsIterator::DecodeLEB128(
-    const CompressedStackMaps& maps,
-    uintptr_t* byte_index) {
-  uword shift = 0;
-  uintptr_t value = 0;
-  uint8_t part = 0;
-  do {
-    ASSERT(*byte_index < maps.payload_size());
-    part = maps.PayloadByte((*byte_index)++);
-    value |= static_cast<uintptr_t>(part & 0x7f) << shift;
-    shift += 7;
-  } while ((part & 0x80) != 0);
-
-  return value;
-}
-
-bool CompressedStackMapsIterator::MoveNext() {
-  // Empty CompressedStackMaps are represented as null values.
-  if (maps_.IsNull() || next_offset_ >= maps_.payload_size()) return false;
-  uintptr_t offset = next_offset_;
-
-  auto const pc_delta = DecodeLEB128(maps_, &offset);
-  ASSERT(pc_delta <= (kMaxUint32 - current_pc_offset_));
-  current_pc_offset_ += pc_delta;
-
-  // Table-using CSMs have a table offset after the PC offset delta, whereas
-  // the post-delta part of inlined entries has the same information as
-  // global table entries.
-  if (maps_.UsesGlobalTable()) {
-    current_global_table_offset_ = DecodeLEB128(maps_, &offset);
-    ASSERT(current_global_table_offset_ < bits_container_.payload_size());
-
-    // Since generally we only use entries in the GC and the GC only needs
-    // the rest of the entry information if the PC offset matches, we lazily
-    // load and cache the information stored in the global object when it is
-    // actually requested.
-    current_spill_slot_bit_count_ = -1;
-    current_non_spill_slot_bit_count_ = -1;
-    current_bits_offset_ = -1;
-  } else {
-    current_spill_slot_bit_count_ = DecodeLEB128(maps_, &offset);
-    ASSERT(current_spill_slot_bit_count_ >= 0);
-
-    current_non_spill_slot_bit_count_ = DecodeLEB128(maps_, &offset);
-    ASSERT(current_non_spill_slot_bit_count_ >= 0);
-
-    const auto stackmap_bits =
-        current_spill_slot_bit_count_ + current_non_spill_slot_bit_count_;
-    const uintptr_t stackmap_size =
-        Utils::RoundUp(stackmap_bits, kBitsPerByte) >> kBitsPerByteLog2;
-    ASSERT(stackmap_size <= (maps_.payload_size() - offset));
-
-    current_bits_offset_ = offset;
-    offset += stackmap_size;
+  if (encoded_bytes_.bytes_written() == 0) {
+    return Object::empty_compressed_stackmaps().raw();
   }
-
-  next_offset_ = offset;
-  return true;
-}
-
-intptr_t CompressedStackMapsIterator::Length() {
-  EnsureFullyLoadedEntry();
-  return current_spill_slot_bit_count_ + current_non_spill_slot_bit_count_;
-}
-intptr_t CompressedStackMapsIterator::SpillSlotBitCount() {
-  EnsureFullyLoadedEntry();
-  return current_spill_slot_bit_count_;
-}
-
-bool CompressedStackMapsIterator::IsObject(intptr_t bit_index) {
-  EnsureFullyLoadedEntry();
-  ASSERT(!bits_container_.IsNull());
-  ASSERT(bit_index >= 0 && bit_index < Length());
-  const intptr_t byte_index = bit_index >> kBitsPerByteLog2;
-  const intptr_t bit_remainder = bit_index & (kBitsPerByte - 1);
-  uint8_t byte_mask = 1U << bit_remainder;
-  const intptr_t byte_offset = current_bits_offset_ + byte_index;
-  return (bits_container_.PayloadByte(byte_offset) & byte_mask) != 0;
-}
-
-void CompressedStackMapsIterator::LazyLoadGlobalTableEntry() {
-  ASSERT(maps_.UsesGlobalTable() && bits_container_.IsGlobalTable());
-  ASSERT(HasLoadedEntry());
-  ASSERT(current_global_table_offset_ < bits_container_.payload_size());
-
-  uintptr_t offset = current_global_table_offset_;
-  current_spill_slot_bit_count_ = DecodeLEB128(bits_container_, &offset);
-  ASSERT(current_spill_slot_bit_count_ >= 0);
-
-  current_non_spill_slot_bit_count_ = DecodeLEB128(bits_container_, &offset);
-  ASSERT(current_non_spill_slot_bit_count_ >= 0);
-
-  const auto stackmap_bits = Length();
-  const uintptr_t stackmap_size =
-      Utils::RoundUp(stackmap_bits, kBitsPerByte) >> kBitsPerByteLog2;
-  ASSERT(stackmap_size <= (bits_container_.payload_size() - offset));
-
-  current_bits_offset_ = offset;
-}
-
-const char* CompressedStackMapsIterator::ToCString(Zone* zone) const {
-  ZoneTextBuffer b(zone, 100);
-  CompressedStackMapsIterator it(*this);
-  // If we haven't loaded an entry yet, do so (but don't skip the current
-  // one if we have!)
-  if (!it.HasLoadedEntry()) {
-    if (!it.MoveNext()) return b.buffer();
-  }
-  bool first_entry = true;
-  do {
-    if (first_entry) {
-      first_entry = false;
-    } else {
-      b.AddString("\n");
-    }
-    b.Printf("0x%08x: ", it.pc_offset());
-    for (intptr_t i = 0, n = it.Length(); i < n; i++) {
-      b.AddString(it.IsObject(i) ? "1" : "0");
-    }
-  } while (it.MoveNext());
-  return b.buffer();
-}
-
-const char* CompressedStackMapsIterator::ToCString() const {
-  return ToCString(Thread::Current()->zone());
+  return CompressedStackMaps::NewInlined(encoded_bytes_.buffer(),
+                                         encoded_bytes_.bytes_written());
 }
 
 ExceptionHandlersPtr ExceptionHandlerList::FinalizeExceptionHandlers(
diff --git a/runtime/vm/code_descriptors.h b/runtime/vm/code_descriptors.h
index bef3ef8..f42190b 100644
--- a/runtime/vm/code_descriptors.h
+++ b/runtime/vm/code_descriptors.h
@@ -18,8 +18,8 @@
 
 class DescriptorList : public ZoneAllocated {
  public:
-  explicit DescriptorList(intptr_t initial_capacity)
-      : encoded_data_(initial_capacity),
+  explicit DescriptorList(Zone* zone)
+      : encoded_data_(zone, kInitialStreamSize),
         prev_pc_offset(0),
         prev_deopt_id(0),
         prev_token_pos(0) {}
@@ -36,7 +36,9 @@
   PcDescriptorsPtr FinalizePcDescriptors(uword entry_point);
 
  private:
-  GrowableArray<uint8_t> encoded_data_;
+  static constexpr intptr_t kInitialStreamSize = 64;
+
+  ZoneWriteStream encoded_data_;
 
   intptr_t prev_pc_offset;
   intptr_t prev_deopt_id;
@@ -47,9 +49,8 @@
 
 class CompressedStackMapsBuilder : public ZoneAllocated {
  public:
-  CompressedStackMapsBuilder() : encoded_bytes_() {}
-
-  static void EncodeLEB128(GrowableArray<uint8_t>* data, uintptr_t value);
+  explicit CompressedStackMapsBuilder(Zone* zone)
+      : encoded_bytes_(zone, kInitialStreamSize) {}
 
   void AddEntry(intptr_t pc_offset,
                 BitmapBuilder* bitmap,
@@ -58,82 +59,13 @@
   CompressedStackMapsPtr Finalize() const;
 
  private:
+  static constexpr intptr_t kInitialStreamSize = 16;
+
+  ZoneWriteStream encoded_bytes_;
   intptr_t last_pc_offset_ = 0;
-  GrowableArray<uint8_t> encoded_bytes_;
   DISALLOW_COPY_AND_ASSIGN(CompressedStackMapsBuilder);
 };
 
-class CompressedStackMapsIterator : public ValueObject {
- public:
-  // We use the null value to represent CompressedStackMaps with no
-  // entries, so any CompressedStackMaps arguments to constructors can be null.
-  CompressedStackMapsIterator(const CompressedStackMaps& maps,
-                              const CompressedStackMaps& global_table);
-  explicit CompressedStackMapsIterator(const CompressedStackMaps& maps);
-
-  explicit CompressedStackMapsIterator(const CompressedStackMapsIterator& it);
-
-  // Loads the next entry from [maps_], if any. If [maps_] is the null
-  // value, this always returns false.
-  bool MoveNext();
-
-  // Finds the entry with the given PC offset starting at the current
-  // position of the iterator. If [maps_] is the null value, this always
-  // returns false.
-  bool Find(uint32_t pc_offset) {
-    // We should never have an entry with a PC offset of 0 inside an
-    // non-empty CSM, so fail.
-    if (pc_offset == 0) return false;
-    do {
-      if (current_pc_offset_ >= pc_offset) break;
-    } while (MoveNext());
-    return current_pc_offset_ == pc_offset;
-  }
-
-  // Methods for accessing parts of an entry should not be called until
-  // a successful MoveNext() or Find() call has been made.
-
-  uint32_t pc_offset() const {
-    ASSERT(HasLoadedEntry());
-    return current_pc_offset_;
-  }
-  // We lazily load and cache information from the global table if the
-  // CSM uses it, so these methods cannot be const.
-  intptr_t Length();
-  intptr_t SpillSlotBitCount();
-  bool IsObject(intptr_t bit_offset);
-
-  void EnsureFullyLoadedEntry() {
-    ASSERT(HasLoadedEntry());
-    if (current_spill_slot_bit_count_ < 0) {
-      LazyLoadGlobalTableEntry();
-    }
-    ASSERT(current_spill_slot_bit_count_ >= 0);
-  }
-
-  const char* ToCString(Zone* zone) const;
-  const char* ToCString() const;
-
- private:
-  static uintptr_t DecodeLEB128(const CompressedStackMaps& data,
-                                uintptr_t* byte_index);
-  bool HasLoadedEntry() const { return next_offset_ > 0; }
-  void LazyLoadGlobalTableEntry();
-
-  const CompressedStackMaps& maps_;
-  const CompressedStackMaps& bits_container_;
-
-  uintptr_t next_offset_ = 0;
-  uint32_t current_pc_offset_ = 0;
-  // Only used when looking up non-PC information in the global table.
-  uintptr_t current_global_table_offset_ = 0;
-  intptr_t current_spill_slot_bit_count_ = -1;
-  intptr_t current_non_spill_slot_bit_count_ = -1;
-  intptr_t current_bits_offset_ = -1;
-
-  friend class StackMapEntry;
-};
-
 class ExceptionHandlerList : public ZoneAllocated {
  public:
   struct HandlerDesc {
diff --git a/runtime/vm/code_descriptors_test.cc b/runtime/vm/code_descriptors_test.cc
index 8c192b5..d8e2c41 100644
--- a/runtime/vm/code_descriptors_test.cc
+++ b/runtime/vm/code_descriptors_test.cc
@@ -100,7 +100,7 @@
   int call_count = 0;
   PcDescriptors::Iterator iter(descriptors,
                                PcDescriptorsLayout::kUnoptStaticCall);
-  CompressedStackMapsBuilder compressed_maps_builder;
+  CompressedStackMapsBuilder compressed_maps_builder(thread->zone());
   while (iter.MoveNext()) {
     compressed_maps_builder.AddEntry(iter.PcOffset(), stack_bitmap, 0);
     ++call_count;
@@ -121,7 +121,7 @@
 }
 
 ISOLATE_UNIT_TEST_CASE(DescriptorList_TokenPositions) {
-  DescriptorList* descriptors = new DescriptorList(64);
+  DescriptorList* descriptors = new DescriptorList(thread->zone());
   ASSERT(descriptors != NULL);
   const intptr_t token_positions[] = {
       kMinInt32,
diff --git a/runtime/vm/compiler/assembler/disassembler.cc b/runtime/vm/compiler/assembler/disassembler.cc
index 0edfb70..e7e73a5 100644
--- a/runtime/vm/compiler/assembler/disassembler.cc
+++ b/runtime/vm/compiler/assembler/disassembler.cc
@@ -220,7 +220,8 @@
                                          const char* function_info,
                                          const Code& code,
                                          bool optimized) {
-  Zone* zone = Thread::Current()->zone();
+  Thread* thread = Thread::Current();
+  Zone* zone = thread->zone();
   LocalVarDescriptors& var_descriptors = LocalVarDescriptors::Handle(zone);
   if (FLAG_print_variable_descriptors) {
     var_descriptors = code.GetLocalVarDescriptors();
@@ -290,13 +291,16 @@
   }
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 
-  THR_Print("StackMaps for function '%s' {\n", function_fullname);
-  if (code.compressed_stackmaps() != CompressedStackMaps::null()) {
+  {
     const auto& stackmaps =
         CompressedStackMaps::Handle(zone, code.compressed_stackmaps());
-    THR_Print("%s\n", stackmaps.ToCString());
+    CompressedStackMaps::Iterator it(thread, stackmaps);
+    TextBuffer buffer(100);
+    buffer.Printf("StackMaps for function '%s' {\n", function_fullname);
+    it.WriteToBuffer(&buffer, "\n");
+    buffer.AddString("}\n");
+    THR_Print("%s", buffer.buffer());
   }
-  THR_Print("}\n");
 
   if (FLAG_print_variable_descriptors) {
     THR_Print("Variable Descriptors for function '%s' {\n", function_fullname);
diff --git a/runtime/vm/compiler/backend/flow_graph_compiler.cc b/runtime/vm/compiler/backend/flow_graph_compiler.cc
index 361ccbe..6a01f8a 100644
--- a/runtime/vm/compiler/backend/flow_graph_compiler.cc
+++ b/runtime/vm/compiler/backend/flow_graph_compiler.cc
@@ -195,7 +195,9 @@
 }
 
 void FlowGraphCompiler::InitCompiler() {
-  pc_descriptors_list_ = new (zone()) DescriptorList(64);
+  compressed_stackmaps_builder_ =
+      new (zone()) CompressedStackMapsBuilder(zone());
+  pc_descriptors_list_ = new (zone()) DescriptorList(zone());
   exception_handlers_list_ = new (zone()) ExceptionHandlerList();
 #if defined(DART_PRECOMPILER)
   catch_entry_moves_maps_builder_ = new (zone()) CatchEntryMovesMapBuilder();
@@ -1001,8 +1003,8 @@
       bitmap->Set(bitmap->Length(), true);
     }
 
-    compressed_stackmaps_builder()->AddEntry(assembler()->CodeSize(), bitmap,
-                                             spill_area_size);
+    compressed_stackmaps_builder_->AddEntry(assembler()->CodeSize(), bitmap,
+                                            spill_area_size);
   }
 }
 
@@ -1157,15 +1159,11 @@
 }
 
 void FlowGraphCompiler::FinalizeStackMaps(const Code& code) {
-  if (compressed_stackmaps_builder_ == NULL) {
-    code.set_compressed_stackmaps(
-        CompressedStackMaps::Handle(CompressedStackMaps::null()));
-  } else {
-    // Finalize the compressed stack maps and add it to the code object.
-    const auto& maps =
-        CompressedStackMaps::Handle(compressed_stackmaps_builder_->Finalize());
-    code.set_compressed_stackmaps(maps);
-  }
+  ASSERT(compressed_stackmaps_builder_ != NULL);
+  // Finalize the compressed stack maps and add it to the code object.
+  const auto& maps =
+      CompressedStackMaps::Handle(compressed_stackmaps_builder_->Finalize());
+  code.set_compressed_stackmaps(maps);
 }
 
 void FlowGraphCompiler::FinalizeVarDescriptors(const Code& code) {
diff --git a/runtime/vm/compiler/backend/flow_graph_compiler.h b/runtime/vm/compiler/backend/flow_graph_compiler.h
index 9b1764e..cff19a26 100644
--- a/runtime/vm/compiler/backend/flow_graph_compiler.h
+++ b/runtime/vm/compiler/backend/flow_graph_compiler.h
@@ -1108,13 +1108,6 @@
 
   intptr_t GetOptimizationThreshold() const;
 
-  CompressedStackMapsBuilder* compressed_stackmaps_builder() {
-    if (compressed_stackmaps_builder_ == NULL) {
-      compressed_stackmaps_builder_ = new CompressedStackMapsBuilder();
-    }
-    return compressed_stackmaps_builder_;
-  }
-
 #if defined(DEBUG)
   void FrameStateUpdateWith(Instruction* instr);
   void FrameStatePush(Definition* defn);
diff --git a/runtime/vm/compiler/frontend/bytecode_reader.cc b/runtime/vm/compiler/frontend/bytecode_reader.cc
index e0d3ea9..f130a7a 100644
--- a/runtime/vm/compiler/frontend/bytecode_reader.cc
+++ b/runtime/vm/compiler/frontend/bytecode_reader.cc
@@ -973,7 +973,7 @@
     const ObjectPool& pool = ObjectPool::Handle(Z, bytecode.object_pool());
     AbstractType& handler_type = AbstractType::Handle(Z);
     Array& handler_types = Array::Handle(Z);
-    DescriptorList* pc_descriptors_list = new (Z) DescriptorList(64);
+    DescriptorList* pc_descriptors_list = new (Z) DescriptorList(Z);
     ExceptionHandlerList* exception_handlers_list =
         new (Z) ExceptionHandlerList();
 
diff --git a/runtime/vm/datastream.h b/runtime/vm/datastream.h
index 81f2c82..7da4532 100644
--- a/runtime/vm/datastream.h
+++ b/runtime/vm/datastream.h
@@ -23,16 +23,38 @@
 static const uint8_t kEndByteMarker = (255 - kMaxDataPerByte);
 static const uint8_t kEndUnsignedByteMarker = (255 - kMaxUnsignedDataPerByte);
 
+struct LEB128Constants : AllStatic {
+  // Convenience template for ensuring non-signed types trigger SFINAE.
+  template <typename T, typename S>
+  using only_if_signed =
+      typename std::enable_if<std::is_signed<T>::value, S>::type;
+
+  // Convenience template for ensuring signed types trigger SFINAE.
+  template <typename T, typename S>
+  using only_if_unsigned =
+      typename std::enable_if<std::is_unsigned<T>::value, S>::type;
+
+  // (S)LEB128 encodes 7 bits of data per byte (hence 128).
+  static constexpr uint8_t kDataBitsPerByte = 7;
+  static constexpr uint8_t kDataByteMask = (1 << kDataBitsPerByte) - 1;
+  // If more data follows a given data byte, the high bit is set.
+  static constexpr uint8_t kMoreDataMask = (1 << kDataBitsPerByte);
+  // For SLEB128, the high bit in the data of the last byte is the sign bit.
+  static constexpr uint8_t kSignMask = (1 << (kDataBitsPerByte - 1));
+};
+
+class NonStreamingWriteStream;
+
 // Stream for reading various types from a buffer.
 class ReadStream : public ValueObject {
  public:
   ReadStream(const uint8_t* buffer, intptr_t size)
       : buffer_(buffer), current_(buffer), end_(buffer + size) {}
 
-  void SetStream(const uint8_t* buffer, intptr_t size) {
-    buffer_ = buffer;
-    current_ = buffer;
-    end_ = buffer + size;
+  // Creates a ReadStream that starts at a given position in the buffer.
+  ReadStream(const uint8_t* buffer, intptr_t size, intptr_t pos)
+      : ReadStream(buffer, size) {
+    SetPosition(pos);
   }
 
   template <int N, typename T>
@@ -78,7 +100,7 @@
 
   intptr_t Position() const { return current_ - buffer_; }
   void SetPosition(intptr_t value) {
-    ASSERT((end_ - buffer_) > value);
+    ASSERT((end_ - buffer_) >= value);
     current_ = buffer_ + value;
   }
 
@@ -106,19 +128,72 @@
   }
 
   uword ReadWordWith32BitReads() {
-    constexpr intptr_t kNumBytesPerRead32 = sizeof(uint32_t);
-    constexpr intptr_t kNumRead32PerWord = sizeof(uword) / kNumBytesPerRead32;
-    constexpr intptr_t kNumBitsPerRead32 = kNumBytesPerRead32 * kBitsPerByte;
+    constexpr intptr_t kNumRead32PerWord = kBitsPerWord / kBitsPerInt32;
 
     uword value = 0;
     for (intptr_t j = 0; j < kNumRead32PerWord; j++) {
-      const auto partial_value = Raw<kNumBytesPerRead32, uint32_t>::Read(this);
-      value |= (static_cast<uword>(partial_value) << (j * kNumBitsPerRead32));
+      const auto partial_value = Raw<kInt32Size, uint32_t>::Read(this);
+      value |= (static_cast<uword>(partial_value) << (j * kBitsPerInt32));
     }
     return value;
   }
 
  private:
+  using C = LEB128Constants;
+
+ public:
+  template <typename T = uintptr_t>
+  C::only_if_unsigned<T, T> ReadLEB128() {
+    constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
+    T r = 0;
+    uint8_t s = 0;
+    uint8_t b;
+    do {
+      ASSERT(s < kBitsPerT);
+      b = ReadByte();
+      r |= static_cast<T>(b & C::kDataByteMask) << s;
+      s += C::kDataBitsPerByte;
+    } while ((b & C::kMoreDataMask) != 0);
+    ASSERT(s < C::kDataBitsPerByte + kBitsPerT);
+    return r;
+  }
+
+  template <typename T>
+  C::only_if_signed<T, T> ReadLEB128() {
+    return bit_cast<T>(ReadLEB128<typename std::make_unsigned<T>::type>());
+  }
+
+  template <typename T>
+  C::only_if_unsigned<T, T> ReadSLEB128() {
+    constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
+    T r = 0;
+    uint8_t s = 0;
+    uint8_t b;
+    do {
+      ASSERT(s < kBitsPerT);
+      b = ReadByte();
+      r |= static_cast<T>(b & C::kDataByteMask) << s;
+      s += C::kDataBitsPerByte;
+    } while ((b & C::kMoreDataMask) != 0);
+    ASSERT(s < C::kDataBitsPerByte + kBitsPerT);
+    // At this point, [s] contains how many data bits have made it into the
+    // value. If the value is negative and the count of data bits is less than
+    // the size of the value, then we need to extend the sign by setting the
+    // remaining (unset) most significant bits (MSBs).
+    T sign_bits = 0;
+    if ((b & C::kSignMask) != 0 && s < kBitsPerT) {
+      // Create a bitmask for the current data bits and invert it.
+      sign_bits = ~((static_cast<T>(1) << s) - 1);
+    }
+    return r | sign_bits;
+  }
+
+  template <typename T = intptr_t>
+  C::only_if_signed<T, T> ReadSLEB128() {
+    return bit_cast<T>(ReadSLEB128<typename std::make_unsigned<T>::type>());
+  }
+
+ private:
   uint16_t Read16() { return Read16(kEndByteMarker); }
 
   uint32_t Read32() { return Read32(kEndByteMarker); }
@@ -128,11 +203,8 @@
   template <typename T>
   T Read(uint8_t end_byte_marker) {
     using Unsigned = typename std::make_unsigned<T>::type;
-    const uint8_t* c = current_;
-    ASSERT(c < end_);
-    Unsigned b = *c++;
+    Unsigned b = ReadByte();
     if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
       return b - end_byte_marker;
     }
     T r = 0;
@@ -140,159 +212,78 @@
     do {
       r |= static_cast<Unsigned>(b) << s;
       s += kDataBitsPerByte;
-      ASSERT(c < end_);
-      b = *c++;
+      b = ReadByte();
     } while (b <= kMaxUnsignedDataPerByte);
-    current_ = c;
     return r | (static_cast<Unsigned>(b - end_byte_marker) << s);
   }
 
-  uint16_t Read16(uint8_t end_byte_marker) {
-    const uint8_t* c = current_;
-    ASSERT(c < end_);
-    uint16_t b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return b - end_byte_marker;
-    }
-    uint16_t r = b;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint16_t>(b - end_byte_marker) << 7);
-    }
+// Setting up needed variables for the unrolled loop sections below.
+#define UNROLLED_INIT()                                                        \
+  using Unsigned = typename std::make_unsigned<T>::type;                       \
+  Unsigned b = ReadByte();                                                     \
+  if (b > kMaxUnsignedDataPerByte) {                                           \
+    return b - end_byte_marker;                                                \
+  }                                                                            \
+  T r = b;
 
-    r |= b << 7;
-    ASSERT(c < end_);
-    b = *c++;
-    ASSERT(b > kMaxUnsignedDataPerByte);
-    current_ = c;
-    return r | (static_cast<uint16_t>(b - end_byte_marker) << 14);
+// Part of the unrolled loop where the loop may stop, having read the last part,
+// or continue reading.
+#define UNROLLED_BODY(bit_start)                                               \
+  static_assert(bit_start % kDataBitsPerByte == 0,                             \
+                "Bit start must be a multiple of the data bits per byte");     \
+  static_assert(bit_start >= 0 && bit_start < kBitsPerByte * sizeof(T),        \
+                "Starting unrolled body at invalid bit position");             \
+  static_assert(bit_start + kDataBitsPerByte < kBitsPerByte * sizeof(T),       \
+                "Unrolled body should not contain final bits in value");       \
+  b = ReadByte();                                                              \
+  if (b > kMaxUnsignedDataPerByte) {                                           \
+    return r | (static_cast<T>(b - end_byte_marker) << bit_start);             \
+  }                                                                            \
+  r |= b << bit_start;
+
+// The end of the unrolled loop.
+#define UNROLLED_END(bit_start)                                                \
+  static_assert(bit_start % kDataBitsPerByte == 0,                             \
+                "Bit start must be a multiple of the data bits per byte");     \
+  static_assert(bit_start >= 0 && bit_start < kBitsPerByte * sizeof(T),        \
+                "Starting unrolled end at invalid bit position");              \
+  static_assert(bit_start + kDataBitsPerByte >= kBitsPerByte * sizeof(T),      \
+                "Unrolled end does not contain final bits in value");          \
+  b = ReadByte();                                                              \
+  ASSERT(b > kMaxUnsignedDataPerByte);                                         \
+  return r | (static_cast<T>(b - end_byte_marker) << bit_start);
+
+  uint16_t Read16(uint8_t end_byte_marker) {
+    using T = uint16_t;
+    UNROLLED_INIT();
+    UNROLLED_BODY(7);
+    UNROLLED_END(14);
   }
 
   uint32_t Read32(uint8_t end_byte_marker) {
-    const uint8_t* c = current_;
-    ASSERT(c < end_);
-    uint32_t b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return b - end_byte_marker;
-    }
-
-    uint32_t r = b;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint32_t>(b - end_byte_marker) << 7);
-    }
-
-    r |= b << 7;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint32_t>(b - end_byte_marker) << 14);
-    }
-
-    r |= b << 14;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint32_t>(b - end_byte_marker) << 21);
-    }
-
-    r |= b << 21;
-    ASSERT(c < end_);
-    b = *c++;
-    ASSERT(b > kMaxUnsignedDataPerByte);
-    current_ = c;
-    return r | (static_cast<uint32_t>(b - end_byte_marker) << 28);
+    using T = uint32_t;
+    UNROLLED_INIT();
+    UNROLLED_BODY(7);
+    UNROLLED_BODY(14);
+    UNROLLED_BODY(21);
+    UNROLLED_END(28);
   }
 
   uint64_t Read64(uint8_t end_byte_marker) {
-    const uint8_t* c = current_;
-    ASSERT(c < end_);
-    uint64_t b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return b - end_byte_marker;
-    }
-    uint64_t r = b;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 7);
-    }
-
-    r |= b << 7;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 14);
-    }
-
-    r |= b << 14;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 21);
-    }
-
-    r |= b << 21;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 28);
-    }
-
-    r |= b << 28;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 35);
-    }
-
-    r |= b << 35;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 42);
-    }
-
-    r |= b << 42;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 49);
-    }
-
-    r |= b << 49;
-    ASSERT(c < end_);
-    b = *c++;
-    if (b > kMaxUnsignedDataPerByte) {
-      current_ = c;
-      return r | (static_cast<uint64_t>(b - end_byte_marker) << 56);
-    }
-
-    r |= b << 56;
-    ASSERT(c < end_);
-    b = *c++;
-    ASSERT(b > kMaxUnsignedDataPerByte);
-    current_ = c;
-    return r | (static_cast<uint64_t>(b - end_byte_marker) << 63);
+    using T = uint64_t;
+    UNROLLED_INIT();
+    UNROLLED_BODY(7);
+    UNROLLED_BODY(14);
+    UNROLLED_BODY(21);
+    UNROLLED_BODY(28);
+    UNROLLED_BODY(35);
+    UNROLLED_BODY(42);
+    UNROLLED_BODY(49);
+    UNROLLED_BODY(56);
+    UNROLLED_END(63);
   }
 
-  uint8_t ReadByte() {
+  DART_FORCE_INLINE uint8_t ReadByte() {
     ASSERT(current_ < end_);
     return *current_++;
   }
@@ -320,9 +311,11 @@
     const intptr_t position_before = Position();
     const intptr_t position_after = Utils::RoundUp(position_before, alignment);
     const intptr_t length = position_after - position_before;
-    EnsureSpace(length);
-    memset(current_, 0, length);
-    SetPosition(position_after);
+    if (length != 0) {
+      EnsureSpace(length);
+      memset(current_, 0, length);
+      SetPosition(position_after);
+    }
     return length;
   }
 
@@ -362,14 +355,12 @@
   };
 
   void WriteWordWith32BitWrites(uword value) {
-    constexpr intptr_t kNumBytesPerWrite32 = sizeof(uint32_t);
-    constexpr intptr_t kNumWrite32PerWord = sizeof(uword) / kNumBytesPerWrite32;
-    constexpr intptr_t kNumBitsPerWrite32 = kNumBytesPerWrite32 * kBitsPerByte;
+    constexpr intptr_t kNumWrite32PerWord = kBitsPerWord / kBitsPerInt32;
 
-    const uint32_t mask = Utils::NBitMask(kNumBitsPerWrite32);
+    const uint32_t mask = Utils::NBitMask(kBitsPerInt32);
     for (intptr_t j = 0; j < kNumWrite32PerWord; j++) {
-      const uint32_t shifted_value = (value >> (j * kNumBitsPerWrite32));
-      Raw<kNumBytesPerWrite32, uint32_t>::Write(this, shifted_value & mask);
+      const uint32_t shifted_value = (value >> (j * kBitsPerInt32));
+      Raw<kInt32Size, uint32_t>::Write(this, shifted_value & mask);
     }
   }
 
@@ -384,11 +375,11 @@
   }
 
   void WriteBytes(const void* addr, intptr_t len) {
-    EnsureSpace(len);
     if (len != 0) {
+      EnsureSpace(len);
       memmove(current_, addr, len);
+      current_ += len;
     }
-    current_ += len;
   }
 
   void WriteWord(uword value) { WriteFixed(value); }
@@ -406,7 +397,7 @@
     // Measure.
     va_list measure_args;
     va_copy(measure_args, args);
-    intptr_t len = Utils::VSNPrint(NULL, 0, format, measure_args);
+    intptr_t len = Utils::VSNPrint(nullptr, 0, format, measure_args);
     va_end(measure_args);
 
     // Alloc.
@@ -443,6 +434,85 @@
 
   void WriteString(const char* cstr) { WriteBytes(cstr, strlen(cstr)); }
 
+ private:
+  using C = LEB128Constants;
+
+ public:
+  template <typename T>
+  C::only_if_unsigned<T, void> WriteLEB128(T value) {
+    T remainder = value;
+    bool is_last_part;
+    do {
+      uint8_t part = static_cast<uint8_t>(remainder & C::kDataByteMask);
+      remainder >>= C::kDataBitsPerByte;
+      // For unsigned types, we're done when the remainder has no bits set.
+      is_last_part = remainder == static_cast<T>(0);
+      if (!is_last_part) {
+        // Mark this part as a non-final part for this value.
+        part |= C::kMoreDataMask;
+      }
+      WriteByte(part);
+    } while (!is_last_part);
+  }
+
+  template <typename T>
+  C::only_if_signed<T, void> WriteLEB128(T value) {
+    // If we're trying to LEB128 encode a negative value, chances are we should
+    // be using SLEB128 instead.
+    ASSERT(value >= 0);
+    return WriteLEB128(bit_cast<typename std::make_unsigned<T>::type>(value));
+  }
+
+  template <typename T>
+  C::only_if_signed<T, void> WriteSLEB128(T value) {
+    constexpr intptr_t kBitsPerT = kBitsPerByte * sizeof(T);
+    using Unsigned = typename std::make_unsigned<T>::type;
+    // Record whether the original value was negative.
+    const bool is_negative = value < 0;
+    T remainder = value;
+    bool is_last_part;
+    do {
+      uint8_t part = static_cast<uint8_t>(remainder & C::kDataByteMask);
+      remainder >>= C::kDataBitsPerByte;
+      // For signed types, we're done when either:
+      // - the remainder has all bits set and the part's sign bit is set
+      //   for negative values, or
+      // - the remainder has no bits set and the part's sign bit is unset for
+      //   non-negative values.
+      // If the remainder matches but the sign bit does not, we need one more
+      // part to set the sign bit correctly when decoding.
+      if (is_negative) {
+        // Right shifts of negative values in C are not guaranteed to be
+        // arithmetic. For negative values, set the [kDataBitsPerByte] most
+        // significant bits after shifting to ensure the value stays negative.
+        constexpr intptr_t preserved_bits = kBitsPerT - C::kDataBitsPerByte;
+        // The sign extension mask is the inverse of the preserved bits mask.
+        constexpr T sign_extend =
+            ~static_cast<T>((static_cast<Unsigned>(1) << preserved_bits) - 1);
+        // Sign extend for negative values just in case a non-arithmetic right
+        // shift is used by the compiler.
+        remainder |= sign_extend;
+        ASSERT(remainder < 0);  // Remainder should still be negative.
+        is_last_part =
+            remainder == ~static_cast<T>(0) && (part & C::kSignMask) != 0;
+      } else {
+        ASSERT(remainder >= 0);  // Remainder should still be non-negative.
+        is_last_part =
+            (remainder == static_cast<T>(0) && (part & C::kSignMask) == 0);
+      }
+      if (!is_last_part) {
+        // Mark this part as a non-final part for this value.
+        part |= C::kMoreDataMask;
+      }
+      WriteByte(part);
+    } while (!is_last_part);
+  }
+
+  template <typename T>
+  C::only_if_unsigned<T, void> WriteSLEB128(T value) {
+    return WriteSLEB128(bit_cast<typename std::make_signed<T>::type>(value));
+  }
+
  protected:
   void EnsureSpace(intptr_t size_needed) {
     if (Remaining() >= size_needed) return;
@@ -508,10 +578,7 @@
 class MallocWriteStream : public NonStreamingWriteStream {
  public:
   explicit MallocWriteStream(intptr_t initial_size)
-      : NonStreamingWriteStream(initial_size) {
-    // Go ahead and allocate initial space at construction.
-    EnsureSpace(initial_size_);
-  }
+      : NonStreamingWriteStream(initial_size) {}
   ~MallocWriteStream();
 
   // Resets the stream and returns the original buffer, which is now considered
@@ -537,10 +604,7 @@
 class ZoneWriteStream : public NonStreamingWriteStream {
  public:
   ZoneWriteStream(Zone* zone, intptr_t initial_size)
-      : NonStreamingWriteStream(initial_size), zone_(zone) {
-    // Go ahead and allocate initial space at construction.
-    EnsureSpace(initial_size_);
-  }
+      : NonStreamingWriteStream(initial_size), zone_(zone) {}
 
  private:
   virtual void Realloc(intptr_t new_size);
@@ -562,10 +626,7 @@
                                 void* callback_data)
       : BaseWriteStream(initial_capacity),
         callback_(callback),
-        callback_data_(callback_data) {
-    // Go ahead and allocate initial space at construction.
-    EnsureSpace(initial_capacity);
-  }
+        callback_data_(callback_data) {}
   ~StreamingWriteStream();
 
  private:
diff --git a/runtime/vm/elf.cc b/runtime/vm/elf.cc
index 5098285..138d02e 100644
--- a/runtime/vm/elf.cc
+++ b/runtime/vm/elf.cc
@@ -1106,35 +1106,8 @@
         stream_(ASSERT_NOTNULL(stream)),
         table_(table) {}
 
-  void sleb128(intptr_t value) {
-    bool is_last_part = false;
-    while (!is_last_part) {
-      uint8_t part = value & 0x7F;
-      value >>= 7;
-      if ((value == 0 && (part & 0x40) == 0) ||
-          (value == static_cast<intptr_t>(-1) && (part & 0x40) != 0)) {
-        is_last_part = true;
-      } else {
-        part |= 0x80;
-      }
-      stream_->WriteByte(part);
-    }
-  }
-
-  void uleb128(uintptr_t value) {
-    bool is_last_part = false;
-    while (!is_last_part) {
-      uint8_t part = value & 0x7F;
-      value >>= 7;
-      if (value == 0) {
-        is_last_part = true;
-      } else {
-        part |= 0x80;
-      }
-      stream_->WriteByte(part);
-    }
-  }
-
+  void sleb128(intptr_t value) { stream_->WriteSLEB128(value); }
+  void uleb128(uintptr_t value) { stream_->WriteLEB128(value); }
   void u1(uint8_t value) { stream_->WriteByte(value); }
   void u2(uint16_t value) { stream_->WriteFixed(value); }
   void u4(uint32_t value) { stream_->WriteFixed(value); }
diff --git a/runtime/vm/kernel_binary.h b/runtime/vm/kernel_binary.h
index e794427..1b53aaa 100644
--- a/runtime/vm/kernel_binary.h
+++ b/runtime/vm/kernel_binary.h
@@ -290,13 +290,17 @@
   }
 
   intptr_t ReadSLEB128() {
-    const uint8_t* buffer = this->buffer();
-    return Utils::DecodeSLEB128<intptr_t>(buffer, size_, &offset_);
+    ReadStream stream(this->buffer(), size_, offset_);
+    const intptr_t result = stream.ReadSLEB128();
+    offset_ = stream.Position();
+    return result;
   }
 
   int64_t ReadSLEB128AsInt64() {
-    const uint8_t* buffer = this->buffer();
-    return Utils::DecodeSLEB128<int64_t>(buffer, size_, &offset_);
+    ReadStream stream(this->buffer(), size_, offset_);
+    const int64_t result = stream.ReadSLEB128<int64_t>();
+    offset_ = stream.Position();
+    return result;
   }
 
   /**
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 25776cd..bbbca69 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -707,7 +707,7 @@
   *null_type_arguments_ = TypeArguments::null();
   *empty_type_arguments_ = TypeArguments::null();
   *null_abstract_type_ = AbstractType::null();
-  *null_compressed_stack_maps_ = CompressedStackMaps::null();
+  *null_compressed_stackmaps_ = CompressedStackMaps::null();
   *bool_true_ = true_;
   *bool_false_ = false_;
 
@@ -999,6 +999,19 @@
     empty_object_pool_->SetCanonical();
   }
 
+  // Allocate and initialize the empty_compressed_stackmaps instance.
+  {
+    const intptr_t instance_size = CompressedStackMaps::InstanceSize(0);
+    uword address = heap->Allocate(instance_size, Heap::kOld);
+    InitializeObject(address, kCompressedStackMapsCid, instance_size);
+    CompressedStackMaps::initializeHandle(
+        empty_compressed_stackmaps_,
+        static_cast<CompressedStackMapsPtr>(address + kHeapObjectTag));
+    empty_compressed_stackmaps_->StoreNonPointer(
+        &empty_compressed_stackmaps_->raw_ptr()->flags_and_size_, 0);
+    empty_compressed_stackmaps_->SetCanonical();
+  }
+
   // Allocate and initialize the empty_descriptors instance.
   {
     uword address = heap->Allocate(PcDescriptors::InstanceSize(0), Heap::kOld);
@@ -1184,14 +1197,16 @@
   ASSERT(null_function_->IsFunction());
   ASSERT(!null_type_arguments_->IsSmi());
   ASSERT(null_type_arguments_->IsTypeArguments());
-  ASSERT(!null_compressed_stack_maps_->IsSmi());
-  ASSERT(null_compressed_stack_maps_->IsCompressedStackMaps());
+  ASSERT(!null_compressed_stackmaps_->IsSmi());
+  ASSERT(null_compressed_stackmaps_->IsCompressedStackMaps());
   ASSERT(!empty_array_->IsSmi());
   ASSERT(empty_array_->IsArray());
   ASSERT(!zero_array_->IsSmi());
   ASSERT(zero_array_->IsArray());
   ASSERT(!empty_context_scope_->IsSmi());
   ASSERT(empty_context_scope_->IsContextScope());
+  ASSERT(!empty_compressed_stackmaps_->IsSmi());
+  ASSERT(empty_compressed_stackmaps_->IsCompressedStackMaps());
   ASSERT(!empty_descriptors_->IsSmi());
   ASSERT(empty_descriptors_->IsPcDescriptors());
   ASSERT(!empty_var_descriptors_->IsSmi());
@@ -14159,35 +14174,6 @@
   return "InstructionsSection";
 }
 
-// Encode integer |value| in SLEB128 format and store into |data|.
-static void EncodeSLEB128(GrowableArray<uint8_t>* data, intptr_t value) {
-  bool is_last_part = false;
-  while (!is_last_part) {
-    uint8_t part = value & 0x7f;
-    value >>= 7;
-    if ((value == 0 && (part & 0x40) == 0) ||
-        (value == static_cast<intptr_t>(-1) && (part & 0x40) != 0)) {
-      is_last_part = true;
-    } else {
-      part |= 0x80;
-    }
-    data->Add(part);
-  }
-}
-
-// Encode integer in SLEB128 format.
-void PcDescriptors::EncodeInteger(GrowableArray<uint8_t>* data,
-                                  intptr_t value) {
-  return EncodeSLEB128(data, value);
-}
-
-// Decode SLEB128 encoded integer. Update byte_index to the next integer.
-intptr_t PcDescriptors::DecodeInteger(intptr_t* byte_index) const {
-  NoSafepointScope no_safepoint;
-  const uint8_t* data = raw_ptr()->data();
-  return Utils::DecodeSLEB128<intptr_t>(data, Length(), byte_index);
-}
-
 ObjectPoolPtr ObjectPool::New(intptr_t len) {
   ASSERT(Object::object_pool_class() != Class::null());
   if (len < 0 || len > kMaxElements) {
@@ -14300,25 +14286,25 @@
   StoreNonPointer(&raw_ptr()->length_, value);
 }
 
-void PcDescriptors::CopyData(GrowableArray<uint8_t>* delta_encoded_data) {
+void PcDescriptors::CopyData(const void* bytes, intptr_t size) {
   NoSafepointScope no_safepoint;
   uint8_t* data = UnsafeMutableNonPointer(&raw_ptr()->data()[0]);
-  for (intptr_t i = 0; i < delta_encoded_data->length(); ++i) {
-    data[i] = (*delta_encoded_data)[i];
-  }
+  // We're guaranted these memory spaces do not overlap.
+  memcpy(data, bytes, size);  // NOLINT
 }
 
-PcDescriptorsPtr PcDescriptors::New(GrowableArray<uint8_t>* data) {
+PcDescriptorsPtr PcDescriptors::New(const void* delta_encoded_data,
+                                    intptr_t size) {
   ASSERT(Object::pc_descriptors_class() != Class::null());
   Thread* thread = Thread::Current();
   PcDescriptors& result = PcDescriptors::Handle(thread->zone());
   {
-    uword size = PcDescriptors::InstanceSize(data->length());
-    ObjectPtr raw = Object::Allocate(PcDescriptors::kClassId, size, Heap::kOld);
+    ObjectPtr raw = Object::Allocate(
+        PcDescriptors::kClassId, PcDescriptors::InstanceSize(size), Heap::kOld);
     NoSafepointScope no_safepoint;
     result ^= raw;
-    result.SetLength(data->length());
-    result.CopyData(data);
+    result.SetLength(size);
+    result.CopyData(delta_encoded_data, size);
   }
   return result.raw();
 }
@@ -14474,45 +14460,195 @@
 }
 
 intptr_t CompressedStackMaps::Hashcode() const {
+  NoSafepointScope scope;
+  uint8_t* data = UnsafeMutableNonPointer(&raw_ptr()->data()[0]);
+  uint8_t* end = data + payload_size();
   uint32_t hash = payload_size();
-  for (uintptr_t i = 0; i < payload_size(); i++) {
-    uint8_t byte = PayloadByte(i);
-    hash = CombineHashes(hash, byte);
+  for (uint8_t* cursor = data; cursor < end; cursor++) {
+    hash = CombineHashes(hash, *cursor);
   }
   return FinalizeHash(hash, kHashBits);
 }
 
-CompressedStackMapsPtr CompressedStackMaps::New(
-    const GrowableArray<uint8_t>& payload,
-    bool is_global_table,
-    bool uses_global_table) {
+CompressedStackMaps::Iterator::Iterator(const CompressedStackMaps& maps,
+                                        const CompressedStackMaps& global_table)
+    : maps_(maps),
+      bits_container_(maps_.UsesGlobalTable() ? global_table : maps_) {
+  ASSERT(!maps_.IsNull());
+  ASSERT(!bits_container_.IsNull());
+  ASSERT(!maps_.IsGlobalTable());
+  ASSERT(!maps_.UsesGlobalTable() || bits_container_.IsGlobalTable());
+}
+
+CompressedStackMaps::Iterator::Iterator(Thread* thread,
+                                        const CompressedStackMaps& maps)
+    : CompressedStackMaps::Iterator(
+          maps,
+          // Only look up the global table if the map will end up using it.
+          maps.UsesGlobalTable() ? CompressedStackMaps::Handle(
+                                       thread->zone(),
+                                       thread->isolate()
+                                           ->object_store()
+                                           ->canonicalized_stack_map_entries())
+                                 : Object::null_compressed_stackmaps()) {}
+
+CompressedStackMaps::Iterator::Iterator(const CompressedStackMaps::Iterator& it)
+    : maps_(it.maps_),
+      bits_container_(it.bits_container_),
+      next_offset_(it.next_offset_),
+      current_pc_offset_(it.current_pc_offset_),
+      current_global_table_offset_(it.current_global_table_offset_),
+      current_spill_slot_bit_count_(it.current_spill_slot_bit_count_),
+      current_non_spill_slot_bit_count_(it.current_spill_slot_bit_count_),
+      current_bits_offset_(it.current_bits_offset_) {}
+
+bool CompressedStackMaps::Iterator::MoveNext() {
+  if (next_offset_ >= maps_.payload_size()) {
+    return false;
+  }
+
+  NoSafepointScope scope;
+  ReadStream stream(maps_.raw_ptr()->data(), maps_.payload_size(),
+                    next_offset_);
+
+  auto const pc_delta = stream.ReadLEB128();
+  ASSERT(pc_delta <= (kMaxUint32 - current_pc_offset_));
+  current_pc_offset_ += pc_delta;
+
+  // Table-using CSMs have a table offset after the PC offset delta, whereas
+  // the post-delta part of inlined entries has the same information as
+  // global table entries.
+  if (maps_.UsesGlobalTable()) {
+    current_global_table_offset_ = stream.ReadLEB128();
+    ASSERT(current_global_table_offset_ < bits_container_.payload_size());
+
+    // Since generally we only use entries in the GC and the GC only needs
+    // the rest of the entry information if the PC offset matches, we lazily
+    // load and cache the information stored in the global object when it is
+    // actually requested.
+    current_spill_slot_bit_count_ = -1;
+    current_non_spill_slot_bit_count_ = -1;
+    current_bits_offset_ = -1;
+
+    next_offset_ = stream.Position();
+  } else {
+    current_spill_slot_bit_count_ = stream.ReadLEB128();
+    ASSERT(current_spill_slot_bit_count_ >= 0);
+
+    current_non_spill_slot_bit_count_ = stream.ReadLEB128();
+    ASSERT(current_non_spill_slot_bit_count_ >= 0);
+
+    const auto stackmap_bits =
+        current_spill_slot_bit_count_ + current_non_spill_slot_bit_count_;
+    const uintptr_t stackmap_size =
+        Utils::RoundUp(stackmap_bits, kBitsPerByte) >> kBitsPerByteLog2;
+    ASSERT(stackmap_size <= (maps_.payload_size() - stream.Position()));
+
+    current_bits_offset_ = stream.Position();
+    next_offset_ = current_bits_offset_ + stackmap_size;
+  }
+
+  return true;
+}
+
+intptr_t CompressedStackMaps::Iterator::Length() const {
+  EnsureFullyLoadedEntry();
+  return current_spill_slot_bit_count_ + current_non_spill_slot_bit_count_;
+}
+intptr_t CompressedStackMaps::Iterator::SpillSlotBitCount() const {
+  EnsureFullyLoadedEntry();
+  return current_spill_slot_bit_count_;
+}
+
+bool CompressedStackMaps::Iterator::IsObject(intptr_t bit_index) const {
+  EnsureFullyLoadedEntry();
+  ASSERT(bit_index >= 0 && bit_index < Length());
+  const intptr_t byte_index = bit_index >> kBitsPerByteLog2;
+  const intptr_t bit_remainder = bit_index & (kBitsPerByte - 1);
+  uint8_t byte_mask = 1U << bit_remainder;
+  const intptr_t byte_offset = current_bits_offset_ + byte_index;
+  NoSafepointScope scope;
+  return (bits_container_.raw_ptr()->data()[byte_offset] & byte_mask) != 0;
+}
+
+void CompressedStackMaps::Iterator::LazyLoadGlobalTableEntry() const {
+  ASSERT(maps_.UsesGlobalTable());
+  ASSERT(HasLoadedEntry());
+  ASSERT(current_global_table_offset_ < bits_container_.payload_size());
+
+  NoSafepointScope scope;
+  ReadStream stream(bits_container_.raw_ptr()->data(),
+                    bits_container_.payload_size(),
+                    current_global_table_offset_);
+
+  current_spill_slot_bit_count_ = stream.ReadLEB128();
+  ASSERT(current_spill_slot_bit_count_ >= 0);
+
+  current_non_spill_slot_bit_count_ = stream.ReadLEB128();
+  ASSERT(current_non_spill_slot_bit_count_ >= 0);
+
+  const auto stackmap_bits = Length();
+  const uintptr_t stackmap_size =
+      Utils::RoundUp(stackmap_bits, kBitsPerByte) >> kBitsPerByteLog2;
+  ASSERT(stackmap_size <= (bits_container_.payload_size() - stream.Position()));
+
+  current_bits_offset_ = stream.Position();
+}
+
+void CompressedStackMaps::Iterator::WriteToBuffer(BaseTextBuffer* buffer,
+                                                  const char* separator) const {
+  CompressedStackMaps::Iterator it(*this);
+  // If we haven't loaded an entry yet, do so (but don't skip the current
+  // one if we have!)
+  if (!it.HasLoadedEntry()) {
+    if (!it.MoveNext()) return;
+  }
+  bool first_entry = true;
+  do {
+    if (!first_entry) {
+      buffer->AddString(separator);
+    }
+    buffer->Printf("0x%0.8" Px32 ": ", it.pc_offset());
+    for (intptr_t i = 0, n = it.Length(); i < n; i++) {
+      buffer->AddString(it.IsObject(i) ? "1" : "0");
+    }
+    first_entry = false;
+  } while (it.MoveNext());
+}
+
+CompressedStackMapsPtr CompressedStackMaps::New(const void* payload,
+                                                intptr_t size,
+                                                bool is_global_table,
+                                                bool uses_global_table) {
   ASSERT(Object::compressed_stackmaps_class() != Class::null());
   // We don't currently allow both flags to be true.
   ASSERT(!is_global_table || !uses_global_table);
-  auto& result = CompressedStackMaps::Handle();
+  // The canonical empty instance should be used instead.
+  ASSERT(size != 0);
 
-  const uintptr_t payload_size = payload.length();
-  if (!CompressedStackMapsLayout::SizeField::is_valid(payload_size)) {
+  if (!CompressedStackMapsLayout::SizeField::is_valid(size)) {
     FATAL1(
         "Fatal error in CompressedStackMaps::New: "
         "invalid payload size %" Pu "\n",
-        payload_size);
+        size);
   }
+
+  auto& result = CompressedStackMaps::Handle();
   {
     // CompressedStackMaps data objects are associated with a code object,
     // allocate them in old generation.
-    ObjectPtr raw = Object::Allocate(
-        CompressedStackMaps::kClassId,
-        CompressedStackMaps::InstanceSize(payload_size), Heap::kOld);
+    ObjectPtr raw =
+        Object::Allocate(CompressedStackMaps::kClassId,
+                         CompressedStackMaps::InstanceSize(size), Heap::kOld);
     NoSafepointScope no_safepoint;
     result ^= raw;
     result.StoreNonPointer(
         &result.raw_ptr()->flags_and_size_,
         CompressedStackMapsLayout::GlobalTableBit::encode(is_global_table) |
             CompressedStackMapsLayout::UsesTableBit::encode(uses_global_table) |
-            CompressedStackMapsLayout::SizeField::encode(payload_size));
+            CompressedStackMapsLayout::SizeField::encode(size));
     auto cursor = result.UnsafeMutableNonPointer(result.raw_ptr()->data());
-    memcpy(cursor, payload.data(), payload.length());  // NOLINT
+    memcpy(cursor, payload, size);  // NOLINT
   }
 
   ASSERT(!result.IsGlobalTable() || !result.UsesGlobalTable());
@@ -14522,12 +14658,16 @@
 
 const char* CompressedStackMaps::ToCString() const {
   ASSERT(!IsGlobalTable());
+  if (payload_size() == 0) {
+    return "CompressedStackMaps()";
+  }
   auto const t = Thread::Current();
-  auto zone = t->zone();
-  const auto& global_table = CompressedStackMaps::Handle(
-      zone, t->isolate()->object_store()->canonicalized_stack_map_entries());
-  CompressedStackMapsIterator it(*this, global_table);
-  return it.ToCString(zone);
+  CompressedStackMaps::Iterator it(t, *this);
+  ZoneTextBuffer buffer(t->zone(), 100);
+  buffer.AddString("CompressedStackMaps(");
+  it.WriteToBuffer(&buffer, ", ");
+  buffer.AddString(")");
+  return buffer.buffer();
 }
 
 StringPtr LocalVarDescriptors::GetName(intptr_t var_index) const {
@@ -16479,6 +16619,7 @@
     NOT_IN_PRODUCT(result.set_comments(Comments::New(0)));
     NOT_IN_PRODUCT(result.set_compile_timestamp(0));
     result.set_pc_descriptors(Object::empty_descriptors());
+    result.set_compressed_stackmaps(Object::empty_compressed_stackmaps());
   }
   return result.raw();
 }
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index e9a388b..230312a 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -417,12 +417,13 @@
   V(Instance, null_instance)                                                   \
   V(Function, null_function)                                                   \
   V(TypeArguments, null_type_arguments)                                        \
-  V(CompressedStackMaps, null_compressed_stack_maps)                           \
+  V(CompressedStackMaps, null_compressed_stackmaps)                            \
   V(TypeArguments, empty_type_arguments)                                       \
   V(Array, empty_array)                                                        \
   V(Array, zero_array)                                                         \
   V(ContextScope, empty_context_scope)                                         \
   V(ObjectPool, empty_object_pool)                                             \
+  V(CompressedStackMaps, empty_compressed_stackmaps)                           \
   V(PcDescriptors, empty_descriptors)                                          \
   V(LocalVarDescriptors, empty_var_descriptors)                                \
   V(ExceptionHandlers, empty_exception_handlers)                               \
@@ -5705,7 +5706,7 @@
     return RoundedAllocationSize(UnroundedSize(len));
   }
 
-  static PcDescriptorsPtr New(GrowableArray<uint8_t>* delta_encoded_data);
+  static PcDescriptorsPtr New(const void* delta_encoded_data, intptr_t size);
 
   // Verify (assert) assumptions about pc descriptors in debug mode.
   void Verify(const Function& function) const;
@@ -5714,12 +5715,6 @@
 
   void PrintToJSONObject(JSONObject* jsobj, bool ref) const;
 
-  // Encode integer in SLEB128 format.
-  static void EncodeInteger(GrowableArray<uint8_t>* data, intptr_t value);
-
-  // Decode SLEB128 encoded integer. Update byte_index to the next integer.
-  intptr_t DecodeInteger(intptr_t* byte_index) const;
-
   // We would have a VisitPointers function here to traverse the
   // pc descriptors table to visit objects if any in the table.
   // Note: never return a reference to a PcDescriptorsLayout::PcDescriptorRec
@@ -5738,10 +5733,12 @@
           cur_yield_index_(PcDescriptorsLayout::kInvalidYieldIndex) {}
 
     bool MoveNext() {
+      NoSafepointScope scope;
+      ReadStream stream(descriptors_.raw_ptr()->data(), descriptors_.Length(),
+                        byte_index_);
       // Moves to record that matches kind_mask_.
       while (byte_index_ < descriptors_.Length()) {
-        const int32_t kind_and_metadata =
-            descriptors_.DecodeInteger(&byte_index_);
+        const int32_t kind_and_metadata = stream.ReadSLEB128<int32_t>();
         cur_kind_ =
             PcDescriptorsLayout::KindAndMetadata::DecodeKind(kind_and_metadata);
         cur_try_index_ = PcDescriptorsLayout::KindAndMetadata::DecodeTryIndex(
@@ -5750,12 +5747,13 @@
             PcDescriptorsLayout::KindAndMetadata::DecodeYieldIndex(
                 kind_and_metadata);
 
-        cur_pc_offset_ += descriptors_.DecodeInteger(&byte_index_);
+        cur_pc_offset_ += stream.ReadSLEB128();
 
         if (!FLAG_precompiled_mode) {
-          cur_deopt_id_ += descriptors_.DecodeInteger(&byte_index_);
-          cur_token_pos_ += descriptors_.DecodeInteger(&byte_index_);
+          cur_deopt_id_ += stream.ReadSLEB128();
+          cur_token_pos_ += stream.ReadSLEB128();
         }
+        byte_index_ = stream.Position();
 
         if ((cur_kind_ & kind_mask_) != 0) {
           return true;  // Current is valid.
@@ -5816,7 +5814,7 @@
   static PcDescriptorsPtr New(intptr_t length);
 
   void SetLength(intptr_t value) const;
-  void CopyData(GrowableArray<uint8_t>* data);
+  void CopyData(const void* bytes, intptr_t size);
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(PcDescriptors, Object);
   friend class Class;
@@ -5908,46 +5906,117 @@
     return RoundedAllocationSize(UnroundedSize(length));
   }
 
-  bool UsesGlobalTable() const { return !IsNull() && UsesGlobalTable(raw()); }
+  bool UsesGlobalTable() const { return UsesGlobalTable(raw()); }
   static bool UsesGlobalTable(const CompressedStackMapsPtr raw) {
     return CompressedStackMapsLayout::UsesTableBit::decode(
         raw->ptr()->flags_and_size_);
   }
 
-  bool IsGlobalTable() const { return !IsNull() && IsGlobalTable(raw()); }
+  bool IsGlobalTable() const { return IsGlobalTable(raw()); }
   static bool IsGlobalTable(const CompressedStackMapsPtr raw) {
     return CompressedStackMapsLayout::GlobalTableBit::decode(
         raw->ptr()->flags_and_size_);
   }
 
-  static CompressedStackMapsPtr NewInlined(
-      const GrowableArray<uint8_t>& bytes) {
-    return New(bytes, /*is_global_table=*/false, /*uses_global_table=*/false);
+  static CompressedStackMapsPtr NewInlined(const void* payload, intptr_t size) {
+    return New(payload, size, /*is_global_table=*/false,
+               /*uses_global_table=*/false);
   }
-  static CompressedStackMapsPtr NewUsingTable(
-      const GrowableArray<uint8_t>& bytes) {
-    return New(bytes, /*is_global_table=*/false, /*uses_global_table=*/true);
+  static CompressedStackMapsPtr NewUsingTable(const void* payload,
+                                              intptr_t size) {
+    return New(payload, size, /*is_global_table=*/false,
+               /*uses_global_table=*/true);
   }
 
-  static CompressedStackMapsPtr NewGlobalTable(
-      const GrowableArray<uint8_t>& bytes) {
-    return New(bytes, /*is_global_table=*/true, /*uses_global_table=*/false);
+  static CompressedStackMapsPtr NewGlobalTable(const void* payload,
+                                               intptr_t size) {
+    return New(payload, size, /*is_global_table=*/true,
+               /*uses_global_table=*/false);
   }
 
+  class Iterator : public ValueObject {
+   public:
+    Iterator(const CompressedStackMaps& maps,
+             const CompressedStackMaps& global_table);
+    Iterator(Thread* thread, const CompressedStackMaps& maps);
+
+    explicit Iterator(const CompressedStackMaps::Iterator& it);
+
+    // Loads the next entry from [maps_], if any. If [maps_] is the null value,
+    // this always returns false.
+    bool MoveNext();
+
+    // Finds the entry with the given PC offset starting at the current position
+    // of the iterator. If [maps_] is the null value, this always returns false.
+    bool Find(uint32_t pc_offset) {
+      // We should never have an entry with a PC offset of 0 inside an
+      // non-empty CSM, so fail.
+      if (pc_offset == 0) return false;
+      do {
+        if (current_pc_offset_ >= pc_offset) break;
+      } while (MoveNext());
+      return current_pc_offset_ == pc_offset;
+    }
+
+    // Methods for accessing parts of an entry should not be called until
+    // a successful MoveNext() or Find() call has been made.
+
+    // Returns the PC offset of the loaded entry.
+    uint32_t pc_offset() const {
+      ASSERT(HasLoadedEntry());
+      return current_pc_offset_;
+    }
+
+    // Returns the bit length of the loaded entry.
+    intptr_t Length() const;
+    // Returns the number of spill slot bits of the loaded entry.
+    intptr_t SpillSlotBitCount() const;
+    // Returns whether the stack entry represented by the offset contains
+    // a tagged objecet.
+    bool IsObject(intptr_t bit_offset) const;
+
+    void WriteToBuffer(BaseTextBuffer* buffer, const char* separator) const;
+
+   private:
+    bool HasLoadedEntry() const { return next_offset_ > 0; }
+
+    // Caches the corresponding values from the global table in the mutable
+    // fields. We lazily load these as some clients only need the PC offset.
+    void LazyLoadGlobalTableEntry() const;
+
+    void EnsureFullyLoadedEntry() const {
+      ASSERT(HasLoadedEntry());
+      if (current_spill_slot_bit_count_ < 0) {
+        LazyLoadGlobalTableEntry();
+        ASSERT(current_spill_slot_bit_count_ >= 0);
+      }
+    }
+
+    const CompressedStackMaps& maps_;
+    const CompressedStackMaps& bits_container_;
+
+    uintptr_t next_offset_ = 0;
+    uint32_t current_pc_offset_ = 0;
+    // Only used when looking up non-PC information in the global table.
+    uintptr_t current_global_table_offset_ = 0;
+    // Marked as mutable as these fields may be updated with lazily loaded
+    // values from the global table when their associated accessor is called,
+    // but those values will never change for a given entry once loaded..
+    mutable intptr_t current_spill_slot_bit_count_ = -1;
+    mutable intptr_t current_non_spill_slot_bit_count_ = -1;
+    mutable intptr_t current_bits_offset_ = -1;
+
+    friend class StackMapEntry;
+  };
+
  private:
-  static CompressedStackMapsPtr New(const GrowableArray<uint8_t>& bytes,
+  static CompressedStackMapsPtr New(const void* payload,
+                                    intptr_t size,
                                     bool is_global_table,
                                     bool uses_global_table);
 
-  uint8_t PayloadByte(uintptr_t offset) const {
-    ASSERT(offset < payload_size());
-    return raw_ptr()->data()[offset];
-  }
-
   FINAL_HEAP_OBJECT_IMPLEMENTATION(CompressedStackMaps, Object);
   friend class Class;
-  friend class CompressedStackMapsIterator;  // For PayloadByte
-  friend class StackMapEntry;                // For PayloadByte
 };
 
 class ExceptionHandlers : public Object {
@@ -10277,7 +10346,6 @@
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(TypedData, TypedDataBase);
   friend class Class;
-  friend class CompressedStackMapsIterator;
   friend class ExternalTypedData;
   friend class TypedDataView;
 };
diff --git a/runtime/vm/object_test.cc b/runtime/vm/object_test.cc
index 060f484..b0eff0e 100644
--- a/runtime/vm/object_test.cc
+++ b/runtime/vm/object_test.cc
@@ -2788,7 +2788,7 @@
 }
 
 ISOLATE_UNIT_TEST_CASE(PcDescriptors) {
-  DescriptorList* builder = new DescriptorList(0);
+  DescriptorList* builder = new DescriptorList(thread->zone());
 
   // kind, pc_offset, deopt_id, token_pos, try_index, yield_index
   builder->AddDescriptor(PcDescriptorsLayout::kOther, 10, 1, TokenPosition(20),
@@ -2858,7 +2858,7 @@
 }
 
 ISOLATE_UNIT_TEST_CASE(PcDescriptorsLargeDeltas) {
-  DescriptorList* builder = new DescriptorList(0);
+  DescriptorList* builder = new DescriptorList(thread->zone());
 
   // kind, pc_offset, deopt_id, token_pos, try_index
   builder->AddDescriptor(PcDescriptorsLayout::kOther, 100, 1,
diff --git a/runtime/vm/program_visitor.cc b/runtime/vm/program_visitor.cc
index d2e13d2..483ce9b 100644
--- a/runtime/vm/program_visitor.cc
+++ b/runtime/vm/program_visitor.cc
@@ -451,20 +451,18 @@
 
 class StackMapEntry : public ZoneAllocated {
  public:
-  StackMapEntry(Zone* zone, const CompressedStackMapsIterator& it)
+  StackMapEntry(Zone* zone, const CompressedStackMaps::Iterator& it)
       : maps_(CompressedStackMaps::Handle(zone, it.maps_.raw())),
         bits_container_(
             CompressedStackMaps::Handle(zone, it.bits_container_.raw())),
-        spill_slot_bit_count_(it.current_spill_slot_bit_count_),
-        non_spill_slot_bit_count_(it.current_non_spill_slot_bit_count_),
+        // If the map uses the global table, this accessor call ensures the
+        // entry is fully loaded before we retrieve [it.current_bits_offset_].
+        spill_slot_bit_count_(it.SpillSlotBitCount()),
+        non_spill_slot_bit_count_(it.Length() - it.SpillSlotBitCount()),
         bits_offset_(it.current_bits_offset_) {
     ASSERT(!maps_.IsNull() && !maps_.IsGlobalTable());
     ASSERT(!bits_container_.IsNull());
     ASSERT(!maps_.UsesGlobalTable() || bits_container_.IsGlobalTable());
-    // Check that the iterator was fully loaded when we ran the initializing
-    // expressions above. By this point we enter the body of the constructor,
-    // it's too late to run EnsureFullyLoadedEntry().
-    ASSERT(it.HasLoadedEntry());
     ASSERT(it.current_spill_slot_bit_count_ >= 0);
   }
 
@@ -475,8 +473,13 @@
     uint32_t hash = 0;
     hash = CombineHashes(hash, spill_slot_bit_count_);
     hash = CombineHashes(hash, non_spill_slot_bit_count_);
-    for (intptr_t i = 0; i < PayloadLength(); i++) {
-      hash = CombineHashes(hash, PayloadByte(i));
+    {
+      NoSafepointScope scope;
+      auto const start = PayloadData();
+      auto const end = start + PayloadLength();
+      for (auto cursor = start; cursor < end; cursor++) {
+        hash = CombineHashes(hash, *cursor);
+      }
     }
     hash_ = FinalizeHash(hash, kHashBits);
     return hash_;
@@ -490,20 +493,19 @@
     // Since we ensure that bits in the payload that are not part of the
     // actual stackmap data are cleared, we can just compare payloads by byte
     // instead of calling IsObject for each bit.
-    for (intptr_t i = 0; i < PayloadLength(); i++) {
-      if (PayloadByte(i) != other->PayloadByte(i)) return false;
-    }
-    return true;
+    NoSafepointScope scope;
+    return memcmp(PayloadData(), other->PayloadData(), PayloadLength()) == 0;
   }
 
   // Encodes this StackMapEntry to the given array of bytes and returns the
   // initial offset of the entry in the array.
-  intptr_t EncodeTo(GrowableArray<uint8_t>* array) {
-    auto const current_offset = array->length();
-    CompressedStackMapsBuilder::EncodeLEB128(array, spill_slot_bit_count_);
-    CompressedStackMapsBuilder::EncodeLEB128(array, non_spill_slot_bit_count_);
-    for (intptr_t i = 0; i < PayloadLength(); i++) {
-      array->Add(PayloadByte(i));
+  intptr_t EncodeTo(NonStreamingWriteStream* stream) {
+    auto const current_offset = stream->Position();
+    stream->WriteLEB128(spill_slot_bit_count_);
+    stream->WriteLEB128(non_spill_slot_bit_count_);
+    {
+      NoSafepointScope scope;
+      stream->WriteBytes(PayloadData(), PayloadLength());
     }
     return current_offset;
   }
@@ -518,8 +520,9 @@
   intptr_t PayloadLength() const {
     return Utils::RoundUp(Length(), kBitsPerByte) >> kBitsPerByteLog2;
   }
-  intptr_t PayloadByte(intptr_t offset) const {
-    return bits_container_.PayloadByte(bits_offset_ + offset);
+  const uint8_t* PayloadData() const {
+    ASSERT(!Thread::Current()->IsAtSafepoint());
+    return bits_container_.raw()->ptr()->data() + bits_offset_;
   }
 
   const CompressedStackMaps& maps_;
@@ -577,9 +580,9 @@
 
     void VisitCode(const Code& code) {
       compressed_stackmaps_ = code.compressed_stackmaps();
-      CompressedStackMapsIterator it(compressed_stackmaps_, old_global_table_);
+      CompressedStackMaps::Iterator it(compressed_stackmaps_,
+                                       old_global_table_);
       while (it.MoveNext()) {
-        it.EnsureFullyLoadedEntry();
         auto const entry = new (zone_) StackMapEntry(zone_, it);
         auto const index = entry_indices_.LookupValue(entry);
         if (index < 0) {
@@ -598,7 +601,9 @@
     CompressedStackMapsPtr CreateGlobalTable(
         StackMapEntryIntMap* entry_offsets) {
       ASSERT(entry_offsets->IsEmpty());
-      if (collected_entries_.length() == 0) return CompressedStackMaps::null();
+      if (collected_entries_.length() == 0) {
+        return CompressedStackMaps::null();
+      }
       // First, sort the entries from most used to least used. This way,
       // the most often used CSMs will have the lowest offsets, which means
       // they will be smaller when LEB128 encoded.
@@ -606,16 +611,17 @@
           [](StackMapEntry* const* e1, StackMapEntry* const* e2) {
             return static_cast<int>((*e2)->UsageCount() - (*e1)->UsageCount());
           });
-      GrowableArray<uint8_t> bytes;
+      MallocWriteStream stream(128);
       // Encode the entries and record their offset in the payload. Sorting the
       // entries may have changed their indices, so update those as well.
       for (intptr_t i = 0, n = collected_entries_.length(); i < n; i++) {
         auto const entry = collected_entries_.At(i);
         entry_indices_.Update({entry, i});
-        entry_offsets->Insert({entry, entry->EncodeTo(&bytes)});
+        entry_offsets->Insert({entry, entry->EncodeTo(&stream)});
       }
       const auto& data = CompressedStackMaps::Handle(
-          zone_, CompressedStackMaps::NewGlobalTable(bytes));
+          zone_, CompressedStackMaps::NewGlobalTable(stream.buffer(),
+                                                     stream.bytes_written()));
       return data.raw();
     }
 
@@ -690,19 +696,23 @@
    private:
     // Creates a normalized CSM from the given non-normalized CSM.
     CompressedStackMapsPtr NormalizeEntries(const CompressedStackMaps& maps) {
-      GrowableArray<uint8_t> new_payload;
-      CompressedStackMapsIterator it(maps, old_global_table_);
+      if (maps.payload_size() == 0) {
+        // No entries, so use the canonical empty map.
+        return Object::empty_compressed_stackmaps().raw();
+      }
+      MallocWriteStream new_payload(maps.payload_size());
+      CompressedStackMaps::Iterator it(maps, old_global_table_);
       intptr_t last_offset = 0;
       while (it.MoveNext()) {
-        it.EnsureFullyLoadedEntry();
         StackMapEntry entry(zone_, it);
-        auto const entry_offset = entry_offsets_.LookupValue(&entry);
-        auto const pc_delta = it.pc_offset() - last_offset;
-        CompressedStackMapsBuilder::EncodeLEB128(&new_payload, pc_delta);
-        CompressedStackMapsBuilder::EncodeLEB128(&new_payload, entry_offset);
+        const intptr_t entry_offset = entry_offsets_.LookupValue(&entry);
+        const intptr_t pc_delta = it.pc_offset() - last_offset;
+        new_payload.WriteLEB128(pc_delta);
+        new_payload.WriteLEB128(entry_offset);
         last_offset = it.pc_offset();
       }
-      return CompressedStackMaps::NewUsingTable(new_payload);
+      return CompressedStackMaps::NewUsingTable(new_payload.buffer(),
+                                                new_payload.bytes_written());
     }
 
     const CompressedStackMaps& old_global_table_;
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 5f03f71..498fd5d 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -1847,7 +1847,9 @@
                                     sizeof(flags_and_size_) * kBitsPerByte -
                                         UsesTableBit::kNextBit> {};
 
+  friend class Object;
   friend class ImageWriter;
+  friend class StackMapEntry;
 };
 
 class LocalVarDescriptorsLayout : public ObjectLayout {
diff --git a/runtime/vm/stack_frame.cc b/runtime/vm/stack_frame.cc
index 9c14f6e..9df6e3c 100644
--- a/runtime/vm/stack_frame.cc
+++ b/runtime/vm/stack_frame.cc
@@ -284,7 +284,7 @@
     auto isolate = isolate_group()->isolates_.First();
 
     global_table = isolate->object_store()->canonicalized_stack_map_entries();
-    CompressedStackMapsIterator it(maps, global_table);
+    CompressedStackMaps::Iterator it(maps, global_table);
     const uword start = code.PayloadStart();
     const uint32_t pc_offset = pc() - start;
     if (it.Find(pc_offset)) {
diff --git a/tests/language/least_upper_bound/least_upper_bound_futureor_test.dart b/tests/language/least_upper_bound/least_upper_bound_futureor_test.dart
new file mode 100644
index 0000000..57954ea
--- /dev/null
+++ b/tests/language/least_upper_bound/least_upper_bound_futureor_test.dart
@@ -0,0 +1,531 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import '../static_type_helper.dart';
+
+// Test least upper bound for types involving `FutureOr`.
+
+bool condition = true;
+
+class A {}
+
+class B {}
+
+class C extends B {}
+
+class D extends B {}
+
+class E<T> {}
+
+class F<T> extends E<T> {}
+
+void main() {
+  // Approach: First test operand types (with no occurrence of `FutureOr`)
+  // then test those operands used as type arguments according to the
+  // rules about **UP**(T1, T2) where T1 or T2 is of the form `FutureOr<S>`.
+
+  void f1(int a, String b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<Object>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<Object>>();
+  }
+
+  void f2(FutureOr<int> a, FutureOr<String> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f3(Future<int> a, FutureOr<String> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f4(int a, FutureOr<String> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f5(int a, num b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<num>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<num>>();
+  }
+
+  void f6(FutureOr<int> a, FutureOr<num> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<num>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<num>>>();
+  }
+
+  void f7(Future<int> a, FutureOr<num> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<num>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<num>>>();
+  }
+
+  void f8(int a, FutureOr<num> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<num>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<num>>>();
+  }
+
+  void f9(List<int> a, List<String> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<List<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<List<Object>>>();
+  }
+
+  void f10(FutureOr<List<int>> a, FutureOr<List<String>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+  }
+
+  void f11(Future<List<int>> a, FutureOr<List<String>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+  }
+
+  void f12(List<int> a, FutureOr<List<String>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>>>>();
+  }
+
+  void f13(List<int> a, List<num> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<List<num>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<List<num>>>();
+  }
+
+  void f14(FutureOr<List<int>> a, FutureOr<List<num>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<num>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<num>>>>();
+  }
+
+  void f15(Future<List<int>> a, FutureOr<List<num>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<num>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<num>>>>();
+  }
+
+  void f16(List<int> a, FutureOr<List<num>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<num>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<num>>>>();
+  }
+
+  void f17(dynamic a, void b) {
+    var x = condition ? a : b;
+    /**/ x.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+
+    var y = condition ? b : a;
+    /**/ y.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+  }
+
+  void f18(FutureOr<dynamic> a, FutureOr<void> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<void>>>();
+    if (x is Future) throw 0;
+    /**/ x.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<void>>>();
+    if (y is Future) throw 0;
+    /**/ y.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+  }
+
+  void f19(Future<dynamic> a, FutureOr<void> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<void>>>();
+    if (x is Future) throw 0;
+    /**/ x.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<void>>>();
+    if (y is Future) throw 0;
+    /**/ y.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+  }
+
+  void f20(dynamic a, FutureOr<void> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<void>>>();
+    if (x is Future) throw 0;
+    /**/ x.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<void>>>();
+    if (y is Future) throw 0;
+    /**/ y.toString();
+    //   ^
+    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
+    // [cfe] This expression has type 'void' and can't be used.
+  }
+
+  void f21(A a, B b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<Object>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<Object>>();
+  }
+
+  void f22(FutureOr<A> a, FutureOr<B> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f23(Future<A> a, FutureOr<B> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f24(A a, FutureOr<B> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f25(B a, C b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<B>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<B>>();
+  }
+
+  void f26(FutureOr<B> a, FutureOr<C> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f27(Future<B> a, FutureOr<C> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f28(B a, FutureOr<C> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f29(C a, D b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<B>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<B>>();
+  }
+
+  void f30(FutureOr<C> a, FutureOr<D> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f31(Future<C> a, FutureOr<D> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f32(C a, FutureOr<D> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<B>>>();
+  }
+
+  void f33(E<B> a, E<C> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<E<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<E<B>>>();
+  }
+
+  void f34(FutureOr<E<B>> a, FutureOr<E<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f35(Future<E<B>> a, FutureOr<E<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f36(E<B> a, FutureOr<E<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f37(E<B> a, F<C> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<E<B>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<E<B>>>();
+  }
+
+  void f38(FutureOr<E<B>> a, FutureOr<F<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f39(Future<E<B>> a, FutureOr<F<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f40(E<B> a, FutureOr<F<C>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<E<B>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<E<B>>>>();
+  }
+
+  void f41(int a, String? b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<Object?>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<Object?>>();
+  }
+
+  void f42(FutureOr<int> a, FutureOr<String?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object?>>>();
+  }
+
+  void f43(Future<int> a, FutureOr<String?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object?>>>();
+  }
+
+  void f44(int a, FutureOr<String?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object?>>>();
+  }
+
+  void f45(List<int> a, List<String>? b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<List<Object>?>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<List<Object>?>>();
+  }
+
+  void f46(FutureOr<List<int>> a, FutureOr<List<String>?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+  }
+
+  void f47(Future<List<int>> a, FutureOr<List<String>?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+  }
+
+  void f48(List<int> a, FutureOr<List<String>?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<List<Object>?>>>();
+  }
+
+  void f49(E<C> a, F<B> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<Object>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<Object>>();
+  }
+
+  void f50(FutureOr<E<C>> a, FutureOr<F<B>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f51(Future<E<C>> a, FutureOr<F<B>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f52(E<C> a, FutureOr<F<B>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  // A sample of cases involving nested futures and nullable types.
+
+  void f53(int a, FutureOr<Future<int>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  // Could soundly have been `FutureOr<Future<int>>`.
+  void f54(Future<int> a, FutureOr<Future<int>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Object>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Object>>>();
+  }
+
+  void f55(Future<Future<int>> a, FutureOr<Future<int>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<Future<int>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<Future<int>>>>();
+  }
+
+  void f56(Future<FutureOr<int>> a, FutureOr<Future<int>> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<FutureOr<int>>>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<FutureOr<int>>>>();
+  }
+
+  void f57(Future<int?> a, FutureOr<int>? b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<int?>?>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<int?>?>>();
+  }
+
+  void f58(Future<int>? a, FutureOr<int?> b) {
+    var x = condition ? a : b;
+    x.expectStaticType<Exactly<FutureOr<int?>?>>();
+
+    var y = condition ? b : a;
+    y.expectStaticType<Exactly<FutureOr<int?>?>>();
+  }
+}
diff --git a/tests/language/setter/declaration_test.dart b/tests/language/setter/declaration_test.dart
index 617fc2c..78d5e81 100644
--- a/tests/language/setter/declaration_test.dart
+++ b/tests/language/setter/declaration_test.dart
@@ -21,119 +21,119 @@
 /*space*/ int? set wrongReturnType1(_) => 1;
 //        ^^^^
 // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-// [cfe] unspecified
+// [cfe] The return type of the setter must be 'void' or absent.
 
 /*space*/ FutureOr<void> set wrongReturnType2(_) {}
 //        ^^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-// [cfe] unspecified
+// [cfe] The return type of the setter must be 'void' or absent.
 
 /*space*/ Never set wrongReturnType3(_) => throw 1;
 //        ^^^^^
 // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-// [cfe] unspecified
+// [cfe] The return type of the setter must be 'void' or absent.
 
 int get nonSubtypes1 => 1;
 //      ^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-// [cfe] unspecified
+// [cfe] The type 'int' of the getter 'nonSubtypes1' is not a subtype of the type 'String' of the setter 'nonSubtypes1'.
 set nonSubtypes1(String _) {}
 
 int? get nonSubtypes2 => 1;
 //       ^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-// [cfe] unspecified
+// [cfe] The type 'int?' of the getter 'nonSubtypes2' is not a subtype of the type 'int' of the setter 'nonSubtypes2'.
 set nonSubtypes2(int _) {}
 
 FutureOr<int> get nonSubtypes3 => 1;
 //                ^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-// [cfe] unspecified
+// [cfe] The type 'FutureOr<int>' of the getter 'nonSubtypes3' is not a subtype of the type 'int' of the setter 'nonSubtypes3'.
 set nonSubtypes3(int _) {}
 
 dynamic get nonSubtypes4 => 1;
 //          ^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-// [cfe] unspecified
+// [cfe] The type 'dynamic' of the getter 'nonSubtypes4' is not a subtype of the type 'int' of the setter 'nonSubtypes4'.
 set nonSubtypes4(int _) {}
 
 class C {
   static int? set staticWrongReturnType1(_) => 1;
   //     ^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   static FutureOr<void> set staticWrongReturnType2(_) {}
   //     ^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   static Never set staticWrongReturnType3(_) => throw 1;
   //     ^^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   /*space*/ int? set wrongReturnType1(_) => 1;
   //        ^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   /*space*/ FutureOr<void> set wrongReturnType2(_) {}
   //        ^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   /*space*/ Never set wrongReturnType3(_) => throw 1;
   //        ^^^^^
   // [analyzer] COMPILE_TIME_ERROR.NON_VOID_RETURN_FOR_SETTER
-  // [cfe] unspecified
+  // [cfe] The return type of the setter must be 'void' or absent.
 
   static int get staticNonSubtypes1 => 1;
   //             ^^^^^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'int' of the getter 'C.staticNonSubtypes1' is not a subtype of the type 'String' of the setter 'C.staticNonSubtypes1'.
   static set staticNonSubtypes1(String _) {}
 
   static int? get staticNonSubtypes2 => 1;
   //              ^^^^^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'int?' of the getter 'C.staticNonSubtypes2' is not a subtype of the type 'int' of the setter 'C.staticNonSubtypes2'.
   static set staticNonSubtypes2(int _) {}
 
   static FutureOr<int> get staticNonSubtypes3 => 1;
   //                       ^^^^^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'FutureOr<int>' of the getter 'C.staticNonSubtypes3' is not a subtype of the type 'int' of the setter 'C.staticNonSubtypes3'.
   static set staticNonSubtypes3(int _) {}
 
   static dynamic get staticNonSubtypes4 => 1;
   //                 ^^^^^^^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'dynamic' of the getter 'C.staticNonSubtypes4' is not a subtype of the type 'int' of the setter 'C.staticNonSubtypes4'.
   static set staticNonSubtypes4(int _) {}
 
   int get nonSubtypes1 => 1;
   //      ^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'int' of the getter 'C.nonSubtypes1' is not a subtype of the type 'String' of the setter 'C.nonSubtypes1'.
   set nonSubtypes1(String _) {}
 
   int? get nonSubtypes2 => 1;
   //       ^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'int?' of the getter 'C.nonSubtypes2' is not a subtype of the type 'int' of the setter 'C.nonSubtypes2'.
   set nonSubtypes2(int _) {}
 
   FutureOr<int> get nonSubtypes3 => 1;
   //                ^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'FutureOr<int>' of the getter 'C.nonSubtypes3' is not a subtype of the type 'int' of the setter 'C.nonSubtypes3'.
   set nonSubtypes3(int _) {}
 
   dynamic get nonSubtypes4 => 1;
   //          ^^^^^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_SUBTYPE_SETTER_TYPES
-  // [cfe] unspecified
+  // [cfe] The type 'dynamic' of the getter 'C.nonSubtypes4' is not a subtype of the type 'int' of the setter 'C.nonSubtypes4'.
   set nonSubtypes4(int _) {}
 }
 
diff --git a/tests/language_2/getter/setter_type_test.dart b/tests/language_2/getter/setter_type_test.dart
index a7caee4..c813ca8 100644
--- a/tests/language_2/getter/setter_type_test.dart
+++ b/tests/language_2/getter/setter_type_test.dart
@@ -11,6 +11,7 @@
 int get foo => bar;
 //      ^^^
 // [analyzer] COMPILE_TIME_ERROR.GETTER_NOT_ASSIGNABLE_SETTER_TYPES
+// [cfe] The type 'int' of the getter 'foo' is not assignable to the type 'String' of the setter 'foo'.
 
 void set foo(String str) {
   bar = str.length;
diff --git a/tools/VERSION b/tools/VERSION
index 4bf35e7..005e49e 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 11
 PATCH 0
-PRERELEASE 205
+PRERELEASE 206
 PRERELEASE_PATCH 0
\ No newline at end of file