Typedefs don't support generic arguments yet.

sdk/lib/_internal/compiler/js_lib/js_mirrors.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.
 
 library dart._js_mirrors;
 
 import 'shared/runtime_data.dart' as encoding;
 import 'shared/embedded_names.dart' show
     ALL_CLASSES,
     LAZIES,
@@ skipping 573 matching lines @@
 
 var classMirrors;
 
 TypeMirror reflectClassByName(Symbol symbol, String mangledName) {
   if (classMirrors == null) classMirrors = JsCache.allocate();
   var mirror = JsCache.fetch(classMirrors, mangledName);
   if (mirror != null) return mirror;
   disableTreeShaking();
   int typeArgIndex = mangledName.indexOf("<");
   if (typeArgIndex != -1) {
-    mirror = new JsTypeBoundClassMirror(reflectClassByMangledName(
-        mangledName.substring(0, typeArgIndex)).originalDeclaration,
+    TypeMirror originalDeclaration =
+        reflectClassByMangledName(mangledName.substring(0, typeArgIndex))
+        .originalDeclaration;
+    if (originalDeclaration is JsTypedefMirror) {
+      throw new UnimplementedError();
+    }
+    mirror = new JsTypeBoundClassMirror(originalDeclaration,
         // Remove the angle brackets enclosing the type arguments.
         mangledName.substring(typeArgIndex + 1, mangledName.length - 1));
     JsCache.update(classMirrors, mangledName, mirror);
     return mirror;
   }
   var allClasses = JS_EMBEDDED_GLOBAL('', ALL_CLASSES);
   var constructor = JS('var', '#[#]', allClasses, mangledName);
   if (constructor == null) {
     // Probably an intercepted class.
     // TODO(ahe): How to handle intercepted classes?
@@ skipping 2347 matching lines @@
   // have a part (following a '.') that starts with '_'.
   const int UNDERSCORE = 0x5f;
   if (name.isEmpty) return true;
   int index = -1;
   do {
     if (name.codeUnitAt(index + 1) == UNDERSCORE) return false;
     index = name.indexOf('.', index + 1);
   } while (index >= 0 && index + 1 < name.length);
   return true;
 }