ES6 doesn't need opt-in

Brendan Eich brendan at mozilla.com
Tue Jan 3 12:20:15 PST 2012


On Jan 3, 2012, at 12:16 PM, Allen Wirfs-Brock wrote:

> On Jan 3, 2012, at 12:01 PM, Brendan Eich wrote:
> 
>> On Jan 3, 2012, at 1:29 AM, Andreas Rossberg wrote:
>> 
>>> ...
>> 
>> 
>>> For multi-part scripts we need a way to switch the
>>> _proper_ top-level into extended mode. Or should I not be able to
>>> write (the relevant bits of) a multi-part script in extended mode at
>>> all?
>> 
>> The proposal may have been unclear on this point: the top level would allow as much new syntax and semantics as can be tolerated backwards-compatibly. The hard cases are let, lexical scope in the free-variables-are-errors sense Dave described (extant globals at start of module body are imported), and any runtime shifts we want (completion reform, typeof null).
> 
> I suspect there will also be issue related to legacy function declarations within blocks.

Possibly, given the intersection semantics between IE and its followers and Firefox are such that you can use a function declared in a block after the block ends, if control flow reached the declaration.

Legacy const is less of an issue since IE did not bite that apple.

/be


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