Migrate language block 46 - canonical_const ... char_escape.

tests/language_strong/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.
-
-import "package:expect/expect.dart";
-
-// Test 'expression as Type' casts.
-
-class C {
-  final int foo = 42;
-
-  int val = 0;
-  void inc() {
-    ++val;
-  }
-}
-
-class D extends C {
-  final int bar = 37;
-}
-
-main() {
-  C oc = new C();
-  D od = new D();
-
-  Expect.throws(() => (oc as dynamic).bar, (e) => e is NoSuchMethodError);
-
-  // Casts should always evaluate the left-hand side, if only for its effects.
-  oc.inc() as dynamic;
-  Expect.equals(1, oc.val);
-  oc.inc() as Object;
-  Expect.equals(2, oc.val);
-}