mozilla/rust — pull request #4141 by catamorphism (2012-12-08 07:48:32+00:00)
Title: Print out a more helpful type error message for do-blocks/for-loops

If a do-block body has the wrong type, or a for-loop body has a
non-() type, suggest that the user might have meant the other one.

As per #2817

r? @brson