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

Brendan Eich brendan at
Wed Jan 2 09:39:17 PST 2013

Herby Vojčík wrote:
> Then it naturally follows that you can as well do `let {must:must, 
> ?may:may} = o` which can be shortened.

Yes, that was the syntax we talked about earlier this year, but I think 
CoffeeScript and TypeScript make a case for suffix-?.

> And it can go deeper, since it is Nil.

What is Nil? There is no requirement with ? in the pattern language (on 
the LHS) for the RHS to be of any particular type.

I like Nil, and it may help rescue ?. the existential operator strawman. 
But that is in the expression language, not in the pattern language.


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