Splats in array destructuring for single-item arrays

[matthewwithanm]

I did a search and didn't see anything about this (it doesn't appear to have been brought up in #870), but independent splats in array destructuring assignments seem to have a behavior that's inconsistent with their named cousins:

[a, ..., z] = [1] # a = 1; z = 1
[a, yada..., z] = [1] # a = 1; z = undefined

The latter matches the es6 proposal and is what I expect, while the former feels like a bug.

[GeoffreyBooth]

This is still the case in CS2 now that destructuring compiles to ES syntax. I’m not sure it’s a bug, exactly, and I wonder about the consequences of changing this behavior now. A pull request would be welcome.