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.
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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