fail-fast object destructuring

Brendan Eich brendan at mozilla.org
Fri Jul 6 10:37:38 PDT 2012


Andreas Rossberg wrote:
>
>     We should talk more at this month's TC39 meeting, but I see a
>     sharp divide ahead:
>
>     1. Choose (A), possibly with modification, either rejecting useful
>     pattern matching decisively, or else making its pattern language
>     differ by making prefix-! implicit. But you rejected splitting
>     pattern meaning across destructuring and future pattern-matching,
>     in the last sentence cited above.
>
>     XOR
>
>     2. Choose (B) because future-proofing for pattern matching wants
>     prefix-?, and impose a compatibility break from what we and others
>     implemented, and what most JS users might expect based on JS's
>     carefree imputing of undefined.
>
>
> Agreed.
>
>
>     Comments from es-discuss peanut gallery welcome. 
>
>
>     I could go for 1/A, except for two facts. First, I believe there
>     is a non-trivial body of Firefox JS that depends on imputing
>     undefined. Second, and what is more important: we haven't
>     usability-tested 2/B at all.
>
>
> Did you mean "could go for 2/B" there?
>

Evidently!

I rearranged and renumbered but missed this one. Clearly I meant 2/B. 
I'm a bit unhappy about making such a change so long after implementing 
1/A (without prefix-!). But never mind me -- what do others think?

/be


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