Follow-up to https://chromiumcodereview.appspot.com/11416144/.

sdk/lib/_internal/compiler/implementation/typechecker.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js;
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name => "Type checker";
 
@@ skipping 243 matching lines @@
   const MalformedType(this.element);
 
   TypeKind get kind => TypeKind.MALFORMED_TYPE;
 
   SourceString get name => element.name;
 
   final MalformedTypeElement element;
 
   DartType unalias(Compiler compiler) => this;
 
-  int get hashCode => 1733;
+  int get hashCode => 1733 + 19 * element.hashCode;
 
-  bool operator ==(other) => other is MalformedType;
+  bool operator ==(other) {
+    if (other is !MalformedType) return false;
+    if (!identical(element, other.element)) return false;
+    return true;
+  }
 
   String toString() => name.slowToString();
 }
 
 class InterfaceType extends DartType {
   final ClassElement element;
   final Link<DartType> typeArguments;
 
   InterfaceType(this.element,
                 [this.typeArguments = const Link<DartType>()]) {
@@ skipping 951 matching lines @@
   }
 
   DartType visitStringNode(StringNode node) {
     compiler.unimplemented('visitNode', node: node);
   }
 
   DartType visitLibraryDependency(LibraryDependency node) {
     compiler.unimplemented('visitNode', node: node);
   }
 }