Refutable pattern

[Brendan Eich]

Brendan Eich wrote:
> Sorry if I was a thread-killer, posting four times in a row.
>
> On balance we have:
>
> prefix-? pros:
> * LR(1) grammar without ambiguity or lookahead restriction.

Forgot to add the one Andreas cited:

* Easier to see prefix-? in front of long object or array pattern.

/be

>
> prefix-? cons:
> * ASI hazard if ? starts an intended destructuring assignment expression.
>
> suffix-? pros:
> * Matches CoffeeScript
> * Matches o?.p existential operator 
> (http://wiki.ecmascript.org/doku.php?id=strawman:existential_operator).
>
> suffix-? cons:
> * Requires yet another a lookahead restriction on top of LR(1).
>
> I'm ok either way. I made my best case for suffix-?. Thoughts and 
> comments welcome.
>
> /be
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