Better handling of splat func arguments (prevent v8 deoptimization) #868
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Do we have a test for cases such as |
| list = @"rend#{ left.constructor.display-name }" o, items, rite | ||
| if rite.to-string! is \arguments and not ret | ||
| arg = true | ||
| if left not instanceof Arr then @carp 'arguments can only destructure to array' |
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Ah you got me. A closure is generated in the case of EDIT: of course the following would still generate sub-optimal (but correct) code but IMHO those who actually write this totally deserve it. Indeed they somehow make sense if named, so I'm not going to hack further... [a, ...[b], c] = &
[a, ...[b, ...c], d] = & |
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That's fine, don't rush it! Just wanted to make sure it worked. |
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Thought it was hard but actually there is a simple but inelegant fix. What prevents a good fix boils down to something simple: [a]:b = [.. for til 4]At top level this should not compile to a closure, but it does right now, i.e. #856 (funny I raised this one too). |
`[.. for [to 10]]` is wrongly rewritten by lexer into `[.. for [from 0 to 10]]` (not quite, see below). Patching the lexer could be non-trivial as said rewriting is currently ad-hoc (`forange` in `lexer.ls`, see gkz#854 for discussion). This temporary solution relaxes the grammar and allow the malformed lexer output. Caveat: `[from x to y]` is *not* supported directly from source despite the change in grammar due to the same lexer hack. The `from` is currently considered a literal rather than a `FROM` token. A possibly cleaner solution is to getting rid of `forange` and support `from` elision in a separate lexer rewrite step or in parser instead.
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@gkz is that okay? |
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May 15, 2016
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see #857, jashkenas/coffeescript#3274 for discussion