Support runtime check of function types.

tests/language/function_subtype1_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.
+
+import 'package:expect/expect.dart';
+
+class C<T> {}
+
+typedef _();
+typedef void void_();
+typedef void void_2();
+typedef int int_();
+typedef int int_2();
+typedef Object Object_();
+typedef double double_();
+typedef void void__int(int i);
+typedef int int__int(int i);
+typedef int int__int2(int i);
+typedef int int__Object(Object o);
+typedef Object Object__int(int i);
+typedef int int__double(double d);
+typedef int int__int_int(int i1, int i2);
+typedef void inline_void_(void f());
+typedef void inline_void__int(void f(int i));
+
+main() {
+  // () -> int <: Function
+  Expect.isTrue(new C<int_>() is C<Function>);
+  // Function <: () -> int
+  Expect.isFalse(new C<Function>() is C<int_>);
+  // () -> dynamic <: () -> dynamic
+  Expect.isTrue(new C<_>() is C<_>);
+  // () -> dynamic <: () -> void
+  Expect.isTrue(new C<_>() is C<void_>);
+  // () -> void <: () -> dynamic
+  Expect.isTrue(new C<void_>() is C<_>);
+  // () -> int <: () -> void
+  Expect.isTrue(new C<int_>() is C<void_>);
+  // () -> void <: () -> int
+  Expect.isFalse(new C<void_>() is C<int_>);
+  // () -> void <: () -> void
+  Expect.isTrue(new C<void_>() is C<void_2>);
+  // () -> int <: () -> int
+  Expect.isTrue(new C<int_>() is C<int_2>);
+  // () -> int <: () -> Object
+  Expect.isTrue(new C<int_>() is C<Object_>);
+  // () -> int <: () -> double
+  Expect.isFalse(new C<int_>() is C<double_>);
+  // () -> int <: (int) -> void
+  Expect.isFalse(new C<int_>() is C<void__int>);
+  // () -> void <: (int) -> int
+  Expect.isFalse(new C<void_>() is C<int__int>);
+  // () -> void <: (int) -> void
+  Expect.isFalse(new C<void_>() is C<void__int>);
+  // (int) -> int <: (int) -> int
+  Expect.isTrue(new C<int__int>() is C<int__int2>);
+  // (Object) -> int <: (int) -> Object
+  Expect.isTrue(new C<int__Object>() is C<Object__int>);
+  // (int) -> int <: (double) -> int
+  Expect.isFalse(new C<int__int>() is C<int__double>);
+  // () -> int <: (int) -> int
+  Expect.isFalse(new C<int_>() is C<int__int>);
+  // (int) -> int <: (int,int) -> int
+  Expect.isFalse(new C<int__int>() is C<int__int_int>);
+  // (int,int) -> int <: (int) -> int
+  Expect.isFalse(new C<int__int_int>() is C<int__int>);
+  // (()->void) -> void <: ((int)->void) -> void
+  Expect.isFalse(new C<inline_void_>() is C<inline_void__int>);
+  // ((int)->void) -> void <: (()->void) -> void
+  Expect.isFalse(new C<inline_void__int>() is C<inline_void_>);
+}