On Jan 20, 2013, at 4:46 PM, Brandon Benvie wrote:
> Err I take it back. They can be implemented in terms of private symbols,
> but every access has to be guarded with a hasOwn check which would be
> observable to a Proxy.
Well, proxy observability is the topic of discussion. they wouldn't be
observable via the proposal I floated in an earlier message.
Allen
>
> On Sunday, January 20, 2013, Brandon Benvie wrote:
> On Sunday, January 20, 2013, Allen Wirfs-Brock wrote:
> I'm not sure if you are getting at something other than what I've described
> above. If a @@DateValue private symbol is actually used as the
> implementation of [[DateValue]] then actuality that would happen.
>
> I explored implementing [[DateValue]], [[NumberValue]], etc. as symbols e.g.
> @@DateValue, but this causes observably different behavior from what is
> specified with a.) inheritance, and b.) interaction with proxies.
>
> Object.create(new Date).getDate(); // works but is specified to not work
>
> new Proxy(new Date, {}).getDate(); // works but is specified to not work
>
> Since Proxy is new in ES6 this of course can still be fixed, but to make the
> first case work would be a (probably benign) backward incompatible change and
> isn't going to work cross-engine unless the spec is changed to explicitly
> allow/require it.
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