[Harmony Proxies] Proposal: Property fixing

Mark S. Miller erights at google.com
Thu May 12 19:24:21 PDT 2011

On Thu, May 12, 2011 at 6:48 PM, Allen Wirfs-Brock <allen at wirfs-brock.com>wrote:

> I've come to view the "native object" semantics defined in ES5 section 8 as
> simply one of many possible object semantics that can be supported by the
> core ES language constructs.  Most of the ES built-in object types implement
> some sort of dialect of the "native object" semantics.  DOM objects have
> even greater divergence and arbitrary host objects in some implementation
> can diverge from "native object" semantics in even more ways.  I thing
> Proxies needed to be view as being closer in power to host objects then they
> are to "native objects".

I think this is the central point of agreement. If conforming host objects
can violate it, then it isn't an ES5 invariant. We should be most suspicious
of violating eternal invariants that even conforming ES5 host objects must

>  Given this, it would be great to have a ESObject implementation that
> programmer can refine for the situations where they intend to make not or
> only minor variations form the standard semantics.

Further constraining a handler to only be able to emulate a conforming
native object is a great use for such a wrapper. This use does not invert
the threat model.

> In terms to the core semantics of Proxies, I think we should restrict
> ourselves to the semantics that are required to support the individual
> statements and operators of the core ES language. These are the same
> semantics that are needed to make those statements and operators operate the
> current range of native, built-in, host objects.
> Allen
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