On Feb 18, 2014, at 10:39 AM, Domenic Denicola wrote:
> You can do so in the manner you were always able to in ES5, and you were able
> to do in ES6 before the introduction of @@create. However, what this means is
> that you now allow parastic inheritance again, which @@create was created to
> disallow.
>
> That is, you could have a MapPromiseWeakMap just by doing
>
> ```js
> var obj = {};
> Map.call(obj);
> Promise.call(obj, function () {});
> WeakMap.call(obj);
> ```
>
> So such a "solution" isn't really maintaining the ES6 semantics, since it
> allows strictly more things than ES6 does.
No, even if you removed the checks in Map and Promise and WeakMap that prevent
them from trying to initialize an object that lacks the appropriate internal
slots it still wouldn't work because obj does not have the internal slots
necessary to support the built-in operations upon those objects and
implementations commonly implement such objects in a manner that prevents the
dynamic addition of such slots.
The whole purpose of @@create is to allow implementations to allocate prior to
invoking a constructor the correctly shaped object for built-ins.
Allen
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