Use index in J/KTypeVariable and fix remaining inequivalence

pkg/compiler/lib/src/common_elements.dart

 // Copyright (c) 2014, 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.
 
 // TODO(sigmund): rename and move to common/elements.dart
 library dart2js.type_system;
 
+import 'common.dart';
 import 'common/names.dart' show Identifiers, Uris;
 import 'constants/values.dart';
 import 'elements/entities.dart';
 import 'elements/names.dart' show PublicName;
 import 'elements/types.dart';
 import 'js_backend/backend.dart' show JavaScriptBackend;
 import 'js_backend/constant_system_javascript.dart';
 import 'universe/call_structure.dart' show CallStructure;
 import 'universe/selector.dart' show Selector;
 import 'universe/call_structure.dart';
@@ skipping 1136 matching lines @@
 
   ClassEntity get expectTrustTypeAnnotationsClass {
     _ensureExpectAnnotations();
     return _expectTrustTypeAnnotationsClass;
   }
 
   ClassEntity get expectAssumeDynamicClass {
     _ensureExpectAnnotations();
     return _expectAssumeDynamicClass;
   }
+
+  /// Returns `true` if the implementation of the 'operator ==' [function] is
+  /// known to handle `null` as argument.
+  bool operatorEqHandlesNullArgument(FunctionEntity function) {
+    assert(function.name == '==',
+        failedAt(function, "Unexpected function $function."));
+    ClassEntity cls = function.enclosingClass;
+    return cls == objectClass ||
+        cls == jsInterceptorClass ||
+        cls == jsNullClass;
+  }
 }
 
 /// Interface for accessing libraries, classes and members.
 ///
 /// The element environment makes private and injected members directly
 /// available and should therefore not be used to determine scopes.
 ///
 /// The properties exposed are Dart-centric and should therefore, long-term, not
 /// be used during codegen, expect for mirrors.
 // TODO(johnniwinther): Split this into an element environment and a type query
@@ skipping 136 matching lines @@
   // TODO(johnniwinther): Remove this when the resolver is removed.
   DartType getUnaliasedType(DartType type);
 
   /// Returns `true` if [member] a the synthetic getter `loadLibrary` injected
   /// on deferred libraries.
   bool isDeferredLoadLibraryGetter(MemberEntity member);
 
   /// Returns the metadata constants declared on [member].
   Iterable<ConstantValue> getMemberMetadata(MemberEntity member);
 }