Fix runtimeType for strings, integers and double: return their interface type.

runtime/lib/object.cc

 // Copyright (c) 2011, 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 "vm/bootstrap_natives.h"
 
 #include "vm/exceptions.h"
 #include "vm/heap.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
@@ skipping 75 matching lines @@
       dart_arguments.SetAt(5, array);
     }
   }
   Exceptions::ThrowByType(Exceptions::kNoSuchMethod, dart_arguments);
   return Object::null();
 }
 
 
 DEFINE_NATIVE_ENTRY(Object_runtimeType, 1) {
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
+  // Special handling for following types outside this native.
+  ASSERT(!instance.IsString() && !instance.IsInteger() && !instance.IsDouble());
   const Type& type = Type::Handle(instance.GetType());
   // The static type of null is specified to be the bottom type, however, the
   // runtime type of null is the Null type, which we correctly return here.
   return type.Canonicalize();
 }
 
 
 DEFINE_NATIVE_ENTRY(Object_instanceOf, 5) {
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
   // Instantiator at position 1 is not used. It is passed along so that the call
@@ skipping 95 matching lines @@
 }
 
 
 DEFINE_NATIVE_ENTRY(AbstractType_toString, 1) {
   const AbstractType& type =
       AbstractType::CheckedHandle(arguments->NativeArgAt(0));
   return type.UserVisibleName();
 }
 
 }  // namespace dart