new classes: special construct stub for derived classs and TDZ for `this`.

src/runtime/runtime-classes.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/v8.h"
 
 #include "src/isolate-inl.h"
@@ skipping 89 matching lines @@
       isolate->factory()->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
   map->SetPrototype(prototype_parent);
   map->set_constructor(*constructor);
   Handle<JSObject> prototype = isolate->factory()->NewJSObjectFromMap(map);
 
   Handle<String> name_string = name->IsString()
                                    ? Handle<String>::cast(name)
                                    : isolate->factory()->empty_string();
   constructor->shared()->set_name(*name_string);
 
+  if (FLAG_experimental_classes) {
+    if (!super_class->IsTheHole() && !super_class->IsNull()) {
+      Handle<Code> stub(isolate->builtins()->JSConstructStubForDerived());

[arv (Not doing code reviews), 2015/01/23 15:40:46]

Let me make sure I understand this correctly. We replace the normal construct
stub with one that understands NewTarget.

This makes me think I should use stubs for the default constructors too.

[Dmitry Lomov (no reviews), 2015/01/23 21:08:28]

Correct, although none of stubs yet understand new.target.
They both will eventually (soon).
JSConstructStubForDerived is the one that does not allocate and passes a hole as
receiver.
Correct.
Yes, this patch does not cover default constructors. If you want I can handle
stubs for them here (although I'd prefer a separate patch)

[arv (Not doing code reviews), 2015/01/23 21:37:00]

Lets handle it here in a different patch. I found some other work until this one
lands.

+      constructor->shared()->set_construct_stub(*stub);
+    }
+  }
+
   JSFunction::SetPrototype(constructor, prototype);
   PropertyAttributes attribs =
       static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
   RETURN_FAILURE_ON_EXCEPTION(
       isolate, JSObject::SetOwnPropertyIgnoreAttributes(
                    constructor, isolate->factory()->prototype_string(),
                    prototype, attribs));
 
   // TODO(arv): Only do this conditionally.
   Handle<Symbol> home_object_symbol(isolate->heap()->home_object_symbol());
@@ skipping 315 matching lines @@
   }
 
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::Call(isolate, proto_function, receiver, argc, argv, false));
   return *result;
 }
 }
 }  // namespace v8::internal