Support runtime check of function types.

tests/language/function_subtype_factory1_test.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.
+// Dart test program for constructors and initializers.
+
+// Check function subtyping with type variables in factory constructors.
+
+import 'package:expect/expect.dart';
+
+class C<T> {
+  factory C(void foo(T t)) => new C.internal();
+  C.internal();
+}
+
+void method(String s) {}
+
+void main() {
+  Expect.isNotNull(new C<String>(method));
+  try {
+    new C<bool>(method);
+    Expect.isFalse(isCheckedMode());
+  } catch (e) {
+    Expect.isTrue(isCheckedMode());
+  }
+}
+
+isCheckedMode() {
+  try {
+    var i = 1;
+    String s = i;
+    return false;
+  } catch (e) {
+    return true;
+  }
+}