Ah, good catch :-) it's late. With strict mode on, it definitely fails, and since the property descriptor is nonconfigurable and nonwritable, this is a non-issue.
Don't mind me, I'll just go sit in the corner. On Fri, Feb 6, 2015 at 1:42 AM, Claude Pache <[email protected]> wrote: > I've looked at your fiddle. The following assignment in line 5: > > Symbol.iterator = Symbol('Symbol.iterator') > > should fail (silently if you are not in strict mode), because the > "iterator" property of the Symbol object is not writable. > > Therefore, in the rest of the fiddle, `Symbol.iterator` should refer to > the original @@iterator symbol, not to the replaced one. > (Your fiddle is a good illustration of why one should always run code in > strict mode.) > > But to answer to the specific question: the spec always uses the original > @@iterator symbol, not the current value of `Symbol.iterator`. > > —Claude > > Le 6 févr. 2015 à 10:19, Jordan Harband <[email protected]> a écrit : > > Should a JS engine retain a reference to the original value of well-known > symbols (like Symbol.iterator), or should steps that use > well-known-Symbol-valued properties (like for..of iteration) always do a > dynamic lookup on that value? > > http://jsfiddle.net/hzzo10dm/2/ is a proof of concept that demonstrates > in Chrome 40 that by replacing Symbol.iterator with another symbol, I can > create some weird behavior. > > What is specified to happen to built-in and custom iterables if I do > `Symbol.iterator = Symbol()`? > > What I would expect is that either: > - the original value of Symbol.iterator would forever be the only value > in a realm that could be used to provide an iterator > - or, that whatever the current value of Symbol.iterator, at that moment > that would be the only way to retrieve an iterator on an object, thus > overwriting Symbol.iterator should break all iteration. > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > >
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