fix #27971, implement generic function RTTI

tests/language_strong/generic_typedef_test.dart

Index: tests/language_strong/generic_typedef_test.dart
diff --git a/tests/language_strong/generic_typedef_test.dart b/tests/language_strong/generic_typedef_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..e6ad21e2bae55567ca935115bc789d892389cc2f
--- /dev/null
+++ b/tests/language_strong/generic_typedef_test.dart
@@ -0,0 +1,61 @@
+// Copyright (c) 2017, 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.
+
+import 'package:expect/expect.dart';
+
+
+// Test runtime behavior of generic function typedefs:
+//
+// - use "is" and "as" on them.
+// - get Type values from runtimeType.
+// - pass type parameters from another generic type to them.
+
+typedef A<T> = T Function(T x, T y);
+typedef B = T Function<T>(T x, T y);
+
+typedef C<K> = Map<K, V> Function<V>(K k, V v);
+typedef D = Map<String, V> Function<V>(String k, V v);
+
+class G<Y, Z> {
+  test() {
+    dynamic d = (Y x, Y y) => y;
+    Expect.isTrue(d is A<Y>);
+    Expect.equals(d is A<Z>, Y == Z);
+
+    Expect.isFalse(d is B);
+    Expect.throws(() => d as B);
+
+    d = (Y y, Z z) => <Y, Z>{};
+    Expect.isFalse(d is C<Y>);
+
+    d = <S>(Y y, S s) => <Y, S>{};
+    Expect.isTrue(d is C<Y>);
+    Expect.equals(d is C<Z>, Y == Z);
+    Expect.equals(d is D, Y == String);
+  }
+}
+
+main() {
+  dynamic d = (int x, int y) => x + y;
+  Expect.isTrue(d is A<int>);
+  Expect.equals((d as A<int>)(1, 2), 3);
+
+  Expect.isFalse(d is B);
+  Expect.throws(() => d as B);
+
+  d = <S>(S x, S y) => x is String ? x : y;
+  Expect.isFalse(d is A);
+  Expect.throws(() => d as A);
+
+  Expect.isTrue(d is B);
+  // TODO(jmesserly): Analyzer incorrectly rejects this form:
+  // Expect.equals((d as B)<int>(1, 2), 2);
+  B b = d;
+  Expect.equals(b<int>(1, 2), 2);
+  Expect.equals(b<String>('a', 'b'), 'a');
+
+
+  new G<int, String>().test();
+  new G<String, String>().test();
+}