On Nov 26, 2012, at 10:00 AM, Tom Van Cutsem wrote: > 2012/11/24 Allen Wirfs-Brock <al...@wirfs-brock.com> > > I see that [2] call for filtering __proto__ access in Get/Put handlers. I > think that dealing with it in a Get/SetInheritance handler would be a much > more efficient way to hand this extremely rare operation. Rather than > filtering for it on every property access, an handler that cares only needs > to worry about the actual Get/SetInhertiance. > > Hmm, so you're arguing that proxy.__proto__ would be equivalent to > Object.getPrototypeOf(proxy), and trigger the "getPrototypeOf" trap, rather > than triggering the "get" trap? > > I guess that more accurately reflects the magical behavior of __proto__. > > Paradoxically, this will move the filter check into the proxy implementation > itself, to properly intercept proxy["__proto__"]. On first sight, this seems > to introduce more overhead.
We need to pin down exactly what backwards compatible semantics of "__proto__" we need to provide. My preference would be to recognize expr.__proto__ as a syntactic form with its own runtime semantics. That would exclude things like expr["__proto__"] and I'd be quite happy with that if it does have any real world compat issue. Allen > > Cheers, > Tom
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