Merge the work on Generic Types Reification from 'dart-lang/reify' repo

pkg/kernel/testcases/reify/closure_test.dart

+// Copyright (c) 2016, 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 closure_test;
+
+import 'test_base.dart';
+
+class A {}
+
+class B {}
+
+typedef B A2B(A a);
+typedef A B2A(B b);
+
+bar(A a) {
+  return null;
+}
+
+B baz(a) {
+  return null;
+}
+
+main() {
+  B foo(A a) {
+    return null;
+  }
+
+  A qux(B b) {
+    return null;
+  }
+
+  expectTrue(foo is A2B);
+  expectTrue(qux is! A2B);
+  expectTrue(foo is! B2A);
+  expectTrue(qux is B2A);
+
+  expectTrue(bar is A2B);
+  expectTrue(bar is! B2A);
+  expectTrue(baz is A2B);
+  expectTrue(baz is! B2A);
+
+  var rab = bar;
+  var zab = baz;
+  expectTrue(rab is A2B);
+  expectTrue(rab is! B2A);
+  expectTrue(zab is A2B);
+  expectTrue(zab is! B2A);
+}