rust-lang/rust — pull request #15538 by bgamari (2014-07-08 23:48:12+00:00)
Title: typeck::check::_match: Better error handling

Previously this was an Option::unwrap() which failed for me.
Unfortunately I've since inadvertently worked around the bug and have
been unable to reproduce it. With this patch hopefully the next person
to encounter this will be in a slightly better position to debug it.