Implement for-in loop for proxies.

src/objects.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3909 matching lines @@
     if (!maybe->To<Map>(&new_map)) return maybe;
   }
   new_map->set_is_extensible(false);
   set_map(new_map);
   ASSERT(!map()->is_extensible());
   return new_map;
 }
 
 
 // Tests for the fast common case for property enumeration:
-// - This object and all prototypes has an enum cache (which means that it has
-//   no interceptors and needs no access checks).
+// - This object and all prototypes has an enum cache (which means that
+//   it is no proxy, has no interceptors and needs no access checks).
 // - This object has no elements.
 // - No prototype has enumerable properties/elements.
-bool JSObject::IsSimpleEnum() {
+bool JSReceiver::IsSimpleEnum() {
   Heap* heap = GetHeap();
   for (Object* o = this;
        o != heap->null_value();
        o = JSObject::cast(o)->GetPrototype()) {
+    if (!o->IsJSObject()) return false;
     JSObject* curr = JSObject::cast(o);
     if (!curr->map()->instance_descriptors()->HasEnumCache()) return false;
     ASSERT(!curr->HasNamedInterceptor());
     ASSERT(!curr->HasIndexedInterceptor());
     ASSERT(!curr->IsAccessCheckNeeded());
     if (curr->NumberOfEnumElements() > 0) return false;
     if (curr != this) {
       FixedArray* curr_fixed_array =
           FixedArray::cast(curr->map()->instance_descriptors()->GetEnumCache());
       if (curr_fixed_array->length() > 0) return false;
@@ skipping 8293 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single break point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 } }  // namespace v8::internal