[cfe] Enforce override check on Object.==

This enforces the override check for when Object.== implements through inheritance.

Closes #42199

Change-Id: I1be1f7dd1b188834e239d2256ad4c312257f2950
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/493340
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/source/source_class_builder.dart

@@ -7,7 +7,6 @@ import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart'
     show ClassHierarchy, ClassHierarchyMembers;
 import 'package:kernel/core_types.dart';
-import 'package:kernel/names.dart' show equalsName;
 import 'package:kernel/reference_from_index.dart'
     show IndexedClass, IndexedLibrary;
 import 'package:kernel/src/bounds_checks.dart';
@@ -1744,7 +1743,7 @@ class SourceClassBuilder extends ClassBuilderImpl
         ],
         localMember: localMember,
       );
-    } else if (declaredFunction?.typeParameters != null) {
+    } else if (declaredFunction?.typeParameters.isNotEmpty ?? false) {
       // Since the bound of `interfaceFunction!.parameter[i]` may have changed
       // during substitution, it can affect the nullabilities of the types in
       // the substitution map. The first parameter to
@@ -2088,16 +2087,6 @@ class SourceClassBuilder extends ClassBuilderImpl
       if (interfaceSignatureType != null) {
         interfaceParameterType = interfaceSignatureType.positionalParameters[i];
       }
-      if (i == 0 &&
-          declaredMember.name == equalsName &&
-          declaredParameterType ==
-              types.hierarchy.coreTypes.objectNonNullableRawType &&
-          interfaceParameter.type is DynamicType) {
-        // TODO(johnniwinther): Add check for opt-in overrides of operator ==.
-        // `operator ==` methods in opt-out classes have type
-        // `bool Function(dynamic)`.
-        continue;
-      }
 
       _checkTypes(
         types,

pkg/front_end/testcases/nnbd/issue42199.dart.strong.expect

@@ -1,4 +1,19 @@
 library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42199.dart:5:7: Error: The implementation of '==' in the non-abstract class 'A' does not conform to its interface.
+// class A {
+//       ^
+// sdk/lib/_internal/vm/lib/object_patch.dart:*: Context: The parameter 'other' of the method 'Object.==' has type 'Object', which does not match the corresponding type, 'dynamic', in the overridden method, 'A.=='.
+//  - 'Object' is from 'dart:core'.
+// Change to a supertype of 'dynamic', or, for a covariant parameter, a subtype.
+//   external bool operator ==(Object other);
+//                                    ^
+// pkg/front_end/testcases/nnbd/issue42199.dart:6:12: Context: This is the overridden method ('==').
+//   operator ==(dynamic other);
+//            ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -6,6 +21,6 @@ class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
-  abstract operator ==(dynamic other) → core::bool;
+  abstract erroneous operator ==(dynamic other) → core::bool;
 }
 static method main() → dynamic {}

pkg/front_end/testcases/nnbd/issue42199.dart.strong.modular.expect

@@ -1,4 +1,19 @@
 library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42199.dart:5:7: Error: The implementation of '==' in the non-abstract class 'A' does not conform to its interface.
+// class A {
+//       ^
+// sdk/lib/_internal/vm/lib/object_patch.dart:*: Context: The parameter 'other' of the method 'Object.==' has type 'Object', which does not match the corresponding type, 'dynamic', in the overridden method, 'A.=='.
+//  - 'Object' is from 'dart:core'.
+// Change to a supertype of 'dynamic', or, for a covariant parameter, a subtype.
+//   external bool operator ==(Object other);
+//                                    ^
+// pkg/front_end/testcases/nnbd/issue42199.dart:6:12: Context: This is the overridden method ('==').
+//   operator ==(dynamic other);
+//            ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -6,6 +21,6 @@ class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
-  abstract operator ==(dynamic other) → core::bool;
+  abstract erroneous operator ==(dynamic other) → core::bool;
 }
 static method main() → dynamic {}

pkg/front_end/testcases/nnbd/issue42199.dart.strong.outline.expect

@@ -1,11 +1,26 @@
 library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42199.dart:5:7: Error: The implementation of '==' in the non-abstract class 'A' does not conform to its interface.
+// class A {
+//       ^
+// sdk/lib/_internal/vm/lib/object_patch.dart:*: Context: The parameter 'other' of the method 'Object.==' has type 'Object', which does not match the corresponding type, 'dynamic', in the overridden method, 'A.=='.
+//  - 'Object' is from 'dart:core'.
+// Change to a supertype of 'dynamic', or, for a covariant parameter, a subtype.
+//   external bool operator ==(Object other);
+//                                    ^
+// pkg/front_end/testcases/nnbd/issue42199.dart:6:12: Context: This is the overridden method ('==').
+//   operator ==(dynamic other);
+//            ^
+//
 import self as self;
 import "dart:core" as core;
 
 class A extends core::Object {
   synthetic constructor •() → self::A
     ;
-  abstract operator ==(dynamic other) → core::bool;
+  abstract erroneous operator ==(dynamic other) → core::bool;
 }
 static method main() → dynamic
   ;

pkg/front_end/testcases/nnbd/issue42199.dart.strong.transformed.expect

@@ -1,4 +1,19 @@
 library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42199.dart:5:7: Error: The implementation of '==' in the non-abstract class 'A' does not conform to its interface.
+// class A {
+//       ^
+// sdk/lib/_internal/vm/lib/object_patch.dart:*: Context: The parameter 'other' of the method 'Object.==' has type 'Object', which does not match the corresponding type, 'dynamic', in the overridden method, 'A.=='.
+//  - 'Object' is from 'dart:core'.
+// Change to a supertype of 'dynamic', or, for a covariant parameter, a subtype.
+//   external bool operator ==(Object other);
+//                                    ^
+// pkg/front_end/testcases/nnbd/issue42199.dart:6:12: Context: This is the overridden method ('==').
+//   operator ==(dynamic other);
+//            ^
+//
 import self as self;
 import "dart:core" as core;
 
@@ -6,6 +21,6 @@ class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
-  abstract operator ==(dynamic other) → core::bool;
+  abstract erroneous operator ==(dynamic other) → core::bool;
 }
 static method main() → dynamic {}

sdk/lib/_internal/vm_shared/lib/date_patch.dart

@@ -122,7 +122,7 @@ class DateTime {
   }
 
   @patch
-  bool operator ==(dynamic other) =>
+  bool operator ==(Object other) =>
       other is DateTime &&
       _value == other.microsecondsSinceEpoch &&
       isUtc == other.isUtc;