Generate dynamic type errors according to spec.

tests/language/src/TypeVariableBounds2Test.dart

Index: tests/language/src/TypeVariableBounds2Test.dart
===================================================================
--- tests/language/src/TypeVariableBounds2Test.dart	(revision 5063)
+++ tests/language/src/TypeVariableBounds2Test.dart	(working copy)
@@ -28,7 +28,10 @@
     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>();