Support new malformed types semantics.

tests/language/is_not_class2_test.dart

 // Copyright (c) 2011, 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.
-// Dart test program for catch that we expect a class after an 'is'.
+
+// Dart test program for catch that we expect a class after an 'is'. This is
+// not a negative test since 'aa' is a malformed type and therefore should be
+// treated as dynamic.
 
 class A {
   const A();
 }
 
 class IsNotClass2NegativeTest {
   static testMain() {
     var a = new A();
     var aa = new A();
 
-    if (a is aa) {
+    if (a is aa) { // static warning
       return 0;
     }
     return 0;
   }
 }
 
 main() {
   IsNotClass2NegativeTest.testMain();
 }