2011/8/11 Brendan Eich <[email protected]> > > This seems to miss Sean's point that receiver is never other than the proxy > for get and set. That follows from how native object [[Get]] works in ES5. >
You're right. Using the "get" trap as an example was silly, since it already has access to receiver, which is the proxy. Your comment made me revisit all derived traps again, and I think I found a compelling and easy-to-understand rule for determining whether or not a trap needs access to proxy/receiver: if the trap deals with inherited properties, it needs access to |proxy|. Using that rule, the following traps require access to |proxy|: get, set, getPropertyDescriptor, getPropertyNames, has, enumerate (incidentally, all of these traps are or can be made derived) All other traps deal only with "own" properties, and do not need |proxy|: getOwnPropertyDescriptor, getOwnPropertyNames, defineProperty, delete, fix, hasOwn, keys getPropertyDescriptor and getPropertyNames require access to |proxy| to walk the prototype-chain. The default behavior of get, set, has and enumerate is specified in terms of either or both of these traps, so they also need access to |proxy|. Note that get and set depend on |proxy| for two reasons: 1) to correctly set |this| for accessors, 2) to be able to lookup a property on the prototype chain (via |Object.getPropertyDescriptor(proxy, name)| ) Cheers, Tom
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