Support runtime check of function types.

tests/language/function_subtype_top_level1_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 for top level functions.
+
+import 'package:expect/expect.dart';
+
+typedef int Foo<T>(T a, [String b]);
+typedef int Bar<T>(T a, [String b]);
+typedef int Baz<T>(T a, {String b});
+typedef int Boz<T>(T a);
+
+int foo(bool a, [String b]) => null;
+int baz(bool a, {String b}) => null;
+int boz(bool a, {int b}) => null;
+
+class C<T> {
+  void test(String nameOfT, bool expectedResult) {
+    Expect.equals(expectedResult, foo is Foo<T>, 'foo is Foo<$nameOfT>');
+    Expect.equals(expectedResult, foo is Bar<T>, 'foo is Bar<$nameOfT>');
+    Expect.isFalse(foo is Baz<T>, 'foo is Baz<$nameOfT>');
+    Expect.equals(expectedResult, foo is Boz<T>, 'foo is Boz<$nameOfT>');
+
+    Expect.isFalse(baz is Foo<T>, 'foo is Foo<$nameOfT>');
+    Expect.isFalse(baz is Bar<T>, 'foo is Bar<$nameOfT>');
+    Expect.equals(expectedResult, baz is Baz<T>, 'foo is Baz<$nameOfT>');
+    Expect.equals(expectedResult, baz is Boz<T>, 'foo is Boz<$nameOfT>');
+
+    Expect.isFalse(boz is Foo<T>, 'foo is Foo<$nameOfT>');
+    Expect.isFalse(boz is Bar<T>, 'foo is Bar<$nameOfT>');
+    Expect.isFalse(boz is Baz<T>, 'foo is Baz<$nameOfT>');
+    Expect.equals(expectedResult, boz is Boz<T>, 'foo is Boz<$nameOfT>');
+  }
+}
+
+main() {
+  new C<bool>().test('bool', true);
+  new C<int>().test('int', false);
+  new C().test('dynamic', true);
+}