Allow self referencing typedefs (issue 2490).

tests/language/function_type_alias6_test.dart

Index: tests/language/function_type_alias6_test.dart
===================================================================
--- tests/language/function_type_alias6_test.dart	(revision 0)
+++ tests/language/function_type_alias6_test.dart	(revision 0)
@@ -0,0 +1,11 @@
+// Copyright (c) 2012, 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 for self referencing function type alias.
+
+typedef F(F x);
+
+main() {
+  var func = _(F x) { };
+  Expect.isTrue(func is F);
+}