Substitute types in instances of generic classes.

tests/lib/mirrors/regress_14304_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.
 
-// Test reflection of private functions in core classes.
+// Regression test for Issue 14304.
 
+import "dart:mirrors";
 import "package:expect/expect.dart";
-import "dart:mirrors";
+
+class A<T> {
+  T m() {}
+}
 
 main() {
-  var s = "string";
-  var im = reflect(s);
-  Expect.throws(() => im.invoke(const Symbol("_setAt"), [0, 65]), (e) => e is NoSuchMethodError);
-}
-
+  ClassMirror a = reflectClass(A);
+  TypeVariableMirror t = a.typeVariables[0];
+  MethodMirror m = a.methods.values.single;
+  
+  Expect.equals(t, m.returnType);
+}