[Parser][SR-698][Qol] add diagnostic for trailing ',' in lists

[dduan]

f(a: Int, b: Int) {}
f(1, b: 2,) // this trailing comma now gets a proper diagnostic.

see https://bugs.swift.org/browse/SR-698

[slavapestov]

@swift-ci Please test

[lattner]

Nice - I love the fix, nice and general!

[ddunbar]

Is this a situation we can safely emit a fixit for, if we know we are inside a method call and immediately followed by a ')'?

[dduan]

@ddunbar Is there any special about functions calls, in regard to fixits?

[ddunbar]

No, but I imagined that your improved diagnostic could fire in situations where the fixit would be very likely to be wrong. I'm not familiar enough with the Swift compiler internals to know more...

On Feb 10, 2016, at 8:29 PM, Daniel Duan [email protected] wrote:

@ddunbar https://github.com/ddunbar Is there any special about functions calls, in regard to fixits?

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Reply to this email directly or view it on GitHub #1265 (comment).

[dduan]

Ah, as in, when the user is typing in Xcode, and the ) has been inserted ahead of time?

This may need some testing. Hmm...

[jrose-apple]

I think it's still a net improvement over what we have now. It's going to diagnose either way, and the user doesn't have to accept the fix-it.

[dduan]

I struggle to come up any edge cases. So if any of core team member thinks this is good enough, feel free to merge.