fail-fast object destructuring (don't add more slop to sloppy mode)

Brendan Eich brendan at
Wed Jan 2 13:33:32 PST 2013

Herby Vojčík wrote:
> In the short example you sketched, with case {must, ?may} there is no 
> need to diverge from the destructuring; so I did not even imagine such 
> divergence for the moment.

Should a proxy in the head of a match be able to observe case-by-case 

>> We need to detail how Nil works, how it cannot be wrapped or observed,
>> etc. in order to maintain equivalence.
> In my naive view, [[GetP]] returns Nil, [[SetP]] does nothing, 
> [[Call]] return Nil. But there are sure some nasty details down there. 

Yeah, this is unsafe by design, if the spec has a bug then Nil leaks 
out. Want undefined in ES6, not Nil.


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