Fix access to fields that didn't exist in the class.

tests/language/cast2_test.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.
 // Dart test program for constructors and initializers.
 
-// Exercises issue 2997, missing var or type on field declarations should
-// generate a compile-time error.
+// Test 'expression as Type' casts.
 
-class A {
-  _this;                      /// 01: compile-time error
-  A(x) : this._this = x;      /// 01: continued
+class C {
+  final int foo = 42;
 }
+
+class D extends C {
+  final int bar = 37;
+}
+
 main() {
-  new A(0);                   /// 01: continued
+  Object oc = new C();
+  Object od = new D();
+
+  (oc as Dynamic).bar;  /// 01: runtime error
 }
+
+