Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_2/dynamic_type_helper.dart

+// Copyright (c) 2013, 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.
+
+library dynamic_type_helper;
+
+import 'package:expect/expect.dart';
+
+/// Checks that a dynamic type error is thrown when [f] is executed
+/// and [expectTypeError] is `true`.
+void testDynamicTypeError(bool expectTypeError, f(), [String message]) {
+  if (expectTypeError) {
+    checkDynamicTypeError(f, message);
+  } else {
+    checkNoDynamicTypeError(f, message);
+  }
+}
+
+/// Checks that a dynamic type error is thrown when f is executed.
+void checkDynamicTypeError(f(), [String message]) {
+  message = message != null ? ': $message' : '';
+  try {
+    f();
+    Expect.fail('Missing type error$message.');
+  } on TypeError catch (e) {}
+}
+
+/// Checks that no dynamic type error is thrown when [f] is executed.
+void checkNoDynamicTypeError(f(), [String message]) {
+  message = message != null ? ': $message' : '';
+  try {
+    f();
+  } on TypeError catch (e) {
+    Expect.fail('Unexpected type error$message.');
+  }
+}