[[Extensible]]and Proxies (Was: Proxy.isProxy )

Allen Wirfs-Brock allen at wirfs-brock.com
Fri Jul 15 12:59:37 PDT 2011


On Jul 15, 2011, at 12:47 PM, Brendan Eich wrote:

> On Jul 15, 2011, at 12:38 PM, Allen Wirfs-Brock wrote:
> 
>> On Jul 15, 2011, at 11:16 AM, Allen Wirfs-Brock wrote:
>> 
>>> But can't a Proxy based object do all sorts of nasty back channel stuff even while it maintains the apparent object freeze invariants?
>> 
>> Duh, of course a frozen object really isn't a Proxy any more as currently defined. But is has also lost all useful intercession  derived semantics.
> 
> This may be ok, so long as we can distinguish preventExtensions from seal from freeze, *and* determine the class or constructor used for the newborn object that becomes the proxy. Yes, I'm thinking faithful Array emulation.
> 
> 
>> BTW, if http://wiki.ecmascript.org/doku.php?id=strawman:fixed_properties was extended to support Object.preventExtensions we might not have anything to argue about except perhaps performance issues. 
> 
> Indeed, that helps quite a bit. Glad to hear it.
> 
> But there may be more power needed in the fix trap, per the above Array-proxy test.

Perhaps the fix trap should return the constructor to use or perhaps even the substitute object. 

Allen
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