Adding [[Invoke]] to address issues with methods called on Proxies

Herby Vojčík herby at
Tue Jan 29 10:52:21 PST 2013

Brandon Benvie wrote:
> Responding in this thread since it's a more appropriate place.
> 1.) It complicates the object model, in that it adds a new internal
> method to objects, but it also clarifies it. It falls under the same
> category as [[GetP]] and [[SetP]]: they complicate the object model, but
> they also clarify it and they are only observable to Proxies. All three
> are only observable to Proxies. Proxies are the thing that ultimately
> complicates the object model and these are fallout from it, but most of
> us agree that Proxies are worth it.

Again, why add something that is "only observable to Proxies"? It is an 
exception, and it bring much more complication than straight rule. Such 
an exception is future-unfriendly.

And I do not agree that it clarifies the object model. On the contrary. 
It makes it inconsistent.

   var quux =;, baz);

was always equivalent of Now, it is not.

[[CallProperty]] is bad because it is alternative to [[Get]], in certain 
situations. What is the problem with, instead, doing it (imo) more 
properly, by reifying [[ChooseThis]](receiver, property) or something 
similar? This will not break the above equivalence, since it will be 
present in all oop calls and inside .apply and .call as well.

> 2.) The abstract method Invoke already exists in the spec. This is a
> thing that the ES6 spec, with its deferring to prototypal inheritance
> for some things previously limited to internal properties, needs. Adding
> [[CallProperty]] would probably be a near net-zero change (perhaps a
> net-reduction) in total spec complexity, since Invoke already exists in
> the spec and is largely subsumed by [[CallProperty]].

Special case adds more complexity than extract (imo).
Spec efficiency does not beat complicating semantics.

> On Tue, Jan 29, 2013 at 12:56 PM, Herby Vojčík <herby at
> <mailto:herby at>> wrote:
>     Brandon Benvie wrote:
>         To elaborate, I've realized that my main disagreement with your
>         position
>         (really my care at all with the private discussion) is much better
>         solved by introducing [[CallProperty]]. That is: Proxies currently
>     ... and complicates object model. My main problem with
>     [[CallProperty]] is the discrepancy between [[Get]] (used in
>     [[Get]]+[[Call]]) and [[CallProperty]] (my assumption that by
>     [[CallProperty]] you mean operation that replaces [[Get]]+[[Call]]).
>     I'd solve it otherwise. Let's say that is split to
>     _three_ operations: [[Get]]+[[OopBind]]+[[Call]], where [[OopBind]]
>     resolves this. Then, proxies should only be able to trap [[OopBind]]
>     (but it will still be the same combination, involving trappable
>     [[Get]] at the beginning and ending with (direct) [[Call]]).
>         handle |this| binding of method calls very poorly. I'm all for
>         either
>         removing private or making it *really* private, but Proxies are
>         basically worthless in the private middleground which causes them to
>         break half the time in ES6 code. But [[CallProperty]] fixes the
>         issue in
>         a way that seems acceptable to all parties.
>     Herby

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