Extension types. Report when implemented not extension type superinterface is not a supertype of the representation type erasure.

Change-Id: Ib1f2bfcfe51edb6bcbc54d7165f148810e3df4ab
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/319600
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml

@@ -654,6 +654,8 @@ CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_DISALLOWED_TYPE:
   status: noFix
 CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_ITSELF:
   status: noFix
+CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE:
+  status: noFix
 CompileTimeErrorCode.EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT:
   status: noFix
 CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_DEPENDS_ON_ITSELF:

pkg/analyzer/lib/src/dart/resolver/resolution_visitor.dart

@@ -1648,15 +1648,9 @@ class ResolutionVisitor extends RecursiveAstVisitor<void> {
 
     final type = namedType.typeOrThrow;
 
-    if (declaration is ExtensionTypeDeclaration) {
-      final typeSystem = _libraryElement.typeSystem;
-      if (!typeSystem.isValidExtensionTypeSuperinterface(type)) {
-        _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_DISALLOWED_TYPE,
-          namedType,
-          [type],
-        );
-      }
+    final enclosingElement = _namedTypeResolver.enclosingClass;
+    if (enclosingElement is ExtensionTypeElementImpl) {
+      _verifyExtensionElementImplements(enclosingElement, namedType, type);
       return;
     }
 
@@ -1770,6 +1764,35 @@ class ResolutionVisitor extends RecursiveAstVisitor<void> {
     }
   }
 
+  void _verifyExtensionElementImplements(
+    ExtensionTypeElementImpl declaredElement,
+    NamedTypeImpl node,
+    DartType type,
+  ) {
+    final typeSystem = _libraryElement.typeSystem;
+
+    if (!typeSystem.isValidExtensionTypeSuperinterface(type)) {
+      _errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_DISALLOWED_TYPE,
+        node,
+        [type],
+      );
+      return;
+    }
+
+    if (type.element is! ExtensionTypeElement) {
+      final erasure = declaredElement.typeErasure;
+      if (!typeSystem.isSubtypeOf(erasure, type)) {
+        _errorReporter.reportErrorForNode(
+          CompileTimeErrorCode
+              .EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE,
+          node,
+          [type, erasure],
+        );
+      }
+    }
+  }
+
   void _visitIf(IfElementOrStatementImpl node) {
     var caseClause = node.caseClause;
     if (caseClause != null) {

pkg/analyzer/lib/src/error/codes.g.dart

@@ -1651,6 +1651,17 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
         "Try removing the superinterface that references this extension type.",
   );
 
+  ///  Parameters:
+  ///  0: the implemented not extension type
+  ///  1: the ultimate representation type
+  static const CompileTimeErrorCode
+      EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE = CompileTimeErrorCode(
+    'EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE',
+    "'{0}' is not a supertype of '{1}', the ultimate representation type.",
+    correctionMessage:
+        "Try specifying a different type, or remove the type from the list.",
+  );
+
   ///  Parameters:
   ///  0: the name of the extension type
   ///  1: the name of the conflicting member

pkg/analyzer/lib/src/error/error_code_values.g.dart

@@ -197,6 +197,7 @@ const List<ErrorCode> errorCodeValues = [
   CompileTimeErrorCode.EXTENSION_TYPE_DECLARES_MEMBER_OF_OBJECT,
   CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_DISALLOWED_TYPE,
   CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_ITSELF,
+  CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE,
   CompileTimeErrorCode.EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT,
   CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_DEPENDS_ON_ITSELF,
   CompileTimeErrorCode.EXTERNAL_FIELD_CONSTRUCTOR_INITIALIZER,

pkg/analyzer/messages.yaml

@@ -5082,6 +5082,13 @@ CompileTimeErrorCode:
     problemMessage: "The extension type can't implement itself."
     correctionMessage: Try removing the superinterface that references this extension type.
     comment: No parameters.
+  EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE:
+    problemMessage: "'{0}' is not a supertype of '{1}', the ultimate representation type."
+    correctionMessage: Try specifying a different type, or remove the type from the list.
+    comment: |-
+      Parameters:
+      0: the implemented not extension type
+      1: the ultimate representation type
   EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT:
     problemMessage: "The extension type '{0}' has more than one distinct member named '{1}' from implemented types."
     correctionMessage: Try redeclaring the corresponding member in this extension type.

pkg/analyzer/test/src/diagnostics/extension_type_implements_not_supertype_of_erasure_test.dart

@@ -0,0 +1,52 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/src/error/codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/context_collection_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ExtensionTypeImplementsDisallowedTypeTest);
+  });
+}
+
+@reflectiveTest
+class ExtensionTypeImplementsDisallowedTypeTest
+    extends PubPackageResolutionTest {
+  test_notSupertype() async {
+    await assertErrorsInCode('''
+extension type A(int it) implements String {}
+''', [
+      error(
+          CompileTimeErrorCode
+              .EXTENSION_TYPE_IMPLEMENTS_NOT_SUPERTYPE_OF_ERASURE,
+          36,
+          6),
+    ]);
+  }
+
+  test_supertype2() async {
+    await assertNoErrorsInCode('''
+extension type A(S3 it) implements S1 {}
+class S1 {}
+class S2 extends S1 {}
+class S3 extends S2 {}
+''');
+  }
+
+  test_supertype_erasure() async {
+    await assertNoErrorsInCode('''
+extension type A(int it) {}
+extension type B(A it) implements num {}
+''');
+  }
+
+  test_supertype_interfaceType() async {
+    await assertNoErrorsInCode('''
+extension type A(int it) implements num {}
+''');
+  }
+}

pkg/analyzer/test/src/diagnostics/extension_type_inherited_member_conflict_test.dart

@@ -129,22 +129,26 @@ class ExtensionTypeInheritedMemberConflictTest_notExtension
   test_conflict() async {
     await assertErrorsInCode('''
 class A {
-  int foo() => 0;
+  void foo(int a) {}
 }
 
 class B {
-  String foo() => '0';
+  void foo(String a) {}
 }
 
-extension type C(Object it) implements A, B {}
+class C implements A, B {
+  void foo(Object a) {}
+}
+
+extension type D(C it) implements A, B {}
 ''', [
       error(
         CompileTimeErrorCode.EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT,
-        82,
+        139,
         1,
         contextMessages: [
-          message('/home/test/lib/test.dart', 16, 3),
-          message('/home/test/lib/test.dart', 50, 3),
+          message('/home/test/lib/test.dart', 17, 3),
+          message('/home/test/lib/test.dart', 51, 3)
         ],
       ),
     ]);
@@ -153,14 +157,18 @@ extension type C(Object it) implements A, B {}
   test_noConflict_redeclared() async {
     await assertNoErrorsInCode('''
 class A {
-  int foo() => 0;
+  void foo(int a) {}
 }
 
 class B {
-  String foo() => '0';
+  void foo(String a) {}
 }
 
-extension type C(Object it) implements A, B {
+class C implements A, B {
+  void foo(Object a) {}
+}
+
+extension type D(C it) implements A, B {
   void foo() {}
 }
 ''');

pkg/analyzer/test/src/diagnostics/test_all.dart

@@ -250,6 +250,8 @@ import 'extension_type_implements_disallowed_type_test.dart'
     as extension_type_implements_disallowed_type;
 import 'extension_type_implements_itself_test.dart'
     as extension_type_implements_itself;
+import 'extension_type_implements_not_supertype_of_erasure_test.dart'
+    as extension_type_implements_not_supertype_of_erasure;
 import 'extension_type_inherited_member_conflict_test.dart'
     as extension_type_inherited_member_conflict;
 import 'extension_type_representation_depends_on_itself_test.dart'
@@ -1058,6 +1060,7 @@ main() {
     extension_type_declares_member_of_object.main();
     extension_type_implements_disallowed_type.main();
     extension_type_implements_itself.main();
+    extension_type_implements_not_supertype_of_erasure.main();
     extension_type_inherited_member_conflict.main();
     extension_type_representation_depends_on_itself.main();
     external_field_constructor_initializer.main();