On Jan 3, 2012, at 12:28 PM, Gavin Barraclough wrote: > On Jan 3, 2012, at 12:18 PM, Brendan Eich wrote: > >> Maybe. We tried in 2006-2007 and ran into at least this: >> >> https://bugzilla.mozilla.org/show_bug.cgi?id=351515 >> >> where 'yield' was used as a parameter name. I dimly recall 'let' in the wild >> but may be misremembering. Perhaps out of paranoia we made both 'let' and >> 'yield' require version opt-in. >> >> The site that used 'yield' has since been updated to avoid using 'yield'. So >> we could try again to reserve 'let' unconditionally. Heaven knows I've been >> yapping about 'let' as the new 'var' long enough to warn most developers >> away from it! >> >> I discussed this on IRC briefly with Oliver, who seemed game. The only issue >> I see is that nightly builds (WebKit, Chrome, Firefox) don't get enough use >> to do other than find true positives. It would be good to find such 'let' >> usage in the wild, of course, but finding nothing won't give us a green >> light, just lack of a red light. > > Why unconditionally reserve let? - would it not make more sense to handle > this in a contextual fashion if we can do so? – if so, we could introduce > 'let' without any backwards compatibility risk, and retain the option to > promote it to a keyword at a later date.
You're proposing that we require 'let' be only at the start of statements? If so, then destructuring is problematic: foo(); let [x] = y; Did that last line destructure the property named '0' of the object denoted by y into a let-bound x, or was it old, pre-ES6 code that stored y into the x'th element of an object denoted 'let'? In either case the 'let' is at the start of a statement. /be
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