Generate dynamic type errors according to spec.

tests/language/src/TypeVariableBounds2Test.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.
 
 // Test of parameterized types with invalid bounds.
 
 interface I<T extends num> { }
 
 interface J<T> { }
 
@@ skipping 10 matching lines @@
     J j = a;  /// 01: static type error
     K k = a;  /// 02: dynamic type error
 
     // In production mode, A<String> is subtype of I, but error in checked mode.
     var x = a is I;  /// 03: dynamic type error
 
     // In both production and checked modes, A<String> is a subtype of I.
     Expect.isTrue(a is J);  /// 04: static type error
 
     // In both production and checked modes, A<String> is not a subtype of K.
-    Expect.isTrue(a is !K);  /// 05: static type error
+    // However, while unsuccessfully trying to prove that A<String> is a K,
+    // a malformed type is encountered in checked mode, resulting in a dynamic
+    // type error.
+    Expect.isTrue(a is !K);  /// 05: dynamic type error
   }
 
   a = new A<int>();
 
   {
     I i = a;
     J j = a;
     K k = a;  /// 06: dynamic type error
 
     // In both production and checked modes, A<int> is a subtype of I.
     Expect.isTrue(a is I);
 
     // In both production and checked modes, A<int> is a subtype of J.
     Expect.isTrue(a is J);
 
     // In both production and checked modes, A<int> is not a subtype of K.
     Expect.isTrue(a is !K);
   }
 }