Support runtime check of function types.

tests/language/function_subtype_typearg1_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.
 
-// Test that a class with a [call] property does not implement [Function] or
-// a typedef of function type.
+// Check function subtyping of type arguments.
 
 import 'package:expect/expect.dart';
 
-class Call {
-  int get call => 0;
-}
+class C<T> {}
 
-typedef void F();
+class I {}
+class J extends I {}
+
+typedef void f1(C<J> c);
+typedef void f2(C<I> c);
 
 main() {
-  Expect.isFalse(new Call() is Function);
-  Expect.isFalse(new Call() is F);
+  Expect.isTrue(new C<f2>() is C<f1>);
 }