libsyntax: fix for has_test_signature

[blackbeam]

Fix for error: functions used as tests must have signature fn() -> () and error: functions used as benches must have signature fn(&mut Bencher) -> () in case of explicit return type declaration.

Currently

#[test]
fn some_test() -> () {}

will produce:

error: functions used as tests must have signature fn() -> ()

which is definitely wrong.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @brson (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[alexcrichton]

@bors: r+ 3dbac78

[alexcrichton]

@bors: r-

er actually, could you add a test for this case as well?

[blackbeam]

@alexcrichton Not sure that github notifies about added commits. re-r?

[alexcrichton]

@bors: r+ fd02920 rollup

Thanks!

[blackbeam]

@alexcrichton I have just fixed the test. Another WCPGW problem, sorry..

[alexcrichton]

@bors: r+ e5b991a

[frewsxcv]

Needs a rebase

[blackbeam]

All except e5b991a (because of 577c464) was merged by #21582.
I think i should close this.