Make TypedefMirror a direct descendant of TypeMirror.

runtime/lib/mirrors.cc

 // 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.
 
 #include "lib/invocation_mirror.h"
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_entry.h"
 #include "vm/exceptions.h"
 #include "vm/object_store.h"
@@ skipping 723 matching lines @@
 
 DEFINE_NATIVE_ENTRY(Mirrors_makeLocalMirrorSystem, 0) {
   return CreateMirrorSystem();
 }
 
 
 DEFINE_NATIVE_ENTRY(Mirrors_makeLocalClassMirror, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Type, type, arguments->NativeArgAt(0));
   const Class& cls = Class::Handle(type.type_class());
   ASSERT(!cls.IsNull());
-  if (cls.IsDynamicClass() || cls.IsVoidClass()) {
+  if (cls.IsDynamicClass() ||
+      cls.IsVoidClass() ||
+      (cls.IsSignatureClass() && !cls.IsCanonicalSignatureClass())) {
     Exceptions::ThrowArgumentError(type);
     UNREACHABLE();
   }
   const Type& stripped_type = Type::Handle(cls.RareType());
   return CreateClassMirror(cls,
                            stripped_type,
                            Bool::True(),  // is_declaration
                            Object::null_instance());
 }
 
@@ skipping 928 matching lines @@
 }
 
 
 DEFINE_NATIVE_ENTRY(VariableMirror_type, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
   const Field& field = Field::Handle(ref.GetFieldReferent());
   return field.type();
 }
 
 }  // namespace dart