Object extension literal

[itrelease]

#2176 and #1632

[michaelficarra]

So this doesn't appear to actually implement object extension literals, but some .= mutating object extension operator like the one proposed in #880. I'm going to oppose it as an object extension literal, as in #1632, would be a superior language feature. Object extension literals also don't work through mutation, promoting a nice functional style. And no tests?

edit: just read through the object extension literal proposal again, and apparently it does work through mutation :(. That makes me sad. Even more reason to support the Coco style in #1632. No mutation in its semantics.

[itrelease]

I see the difference only in syntax: .= instead of .{ or I'm wrong? I'll add tests tomorrow.

[michaelficarra]

No, you're right. It was my mistake. See my edit above.

[TrevorBurnham]

The branch you're trying to merge appears to have two unrelated changes: The .= syntax, and the attr_reader etc. stuff proposed at #2173. I assume that's unintentional?

Also, no test cases?

[itrelease]

I removed unrelated changes and added test.

[TrevorBurnham]

What's with the scope check? Shouldn't a .= {x: 1} be a legitimate way of extending window.a?

[itrelease]

It will extend variable if it exist in parent scope and throw error if variable wasn't defined.

[TrevorBurnham]

Hmm, well it is consistent with the new strict error on a ?= b et al.

[michaelficarra]

@itrelease: @TrevorBurnham is trying to make the point that we should be able to use this operator on externally-defined variables -- things that are in scope, but which CoffeeScript doesn't know about. This can be any property added to the global object (or anywhere up its prototype chain), since the global object is also the root of the scope chain.

edit: @TrevorBurnham: I don't believe it is. Since it doesn't introduce a variable into scope, it should behave more like += (LHS not in scope is allowed).

[itrelease]

Oh I see, so we should just rely on thing that variable might be in scope and not throwing error?