On 19 July 2012 00:19, Jason Orendorff <jason.orendo...@gmail.com> wrote:
> On Wed, Jul 18, 2012 at 3:31 PM, Brendan Eich <bren...@mozilla.org> wrote: > > In particular, we don't want a proto-chain walk from [[CanPut]] and a > second > > walk from the "has" under the __proto__ setter for > > > > obj.__proto__ = safe; // not in SES code > > > > just because we might need the "has" for > > > > evil = Object.getOwnPropertyDescriptor(Object.prototype, > '__proto__').set; > > > > // later ... > > > > evil.call(victim, unsafe); > > > > How would you spec this? > > I would spec the desired semantics. I really don't think we should > bend the language spec an iota around performance here. > I like Jason's suggestion, and I agree that performance should be the least of all concerns for proto mutation. (In fact, can we perhaps spec it in a way that guarantees that this operation is so expensive that it discourages everybody from still using it in the future? Like, insert a step that says "pause for 10 seconds to reconsider". :) ) /Andreas
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