swift234

If an expression fails to type check, and there were no failures posted or constraints to mine for a reason, we can be fairly certain that the reason for the failure was a lack of contextual type data. In this case, we should post a diagnostic rather than let the failure slip through. This addresses crash suite scenarios 001, 005, 020 and 045. (rdar://problem/16712071, rdar://problem/17317691, rdar://problem/17317691)

You'll notice that emitting this diagnostic will make some already noisy closure-related errors slightly more so. This is unfortunate, but for the time-being it's better than crashing.

Swift SVN r21817