scala/scala — pull request #1490 by paulp (2012-10-10 22:08:18+00:00)
Title: Fix for SI-6499, regression in type inference.

I can't do any better than a reproduced comment:

For some reason which is still a bit fuzzy, we must let Nothing
through as a lower bound despite the fact that Nothing is always
a lower bound. My current supposition is that the side-effecting
type constraint accumulation mechanism depends on these subtype
tests being performed to make forward progress when there are
mutally recursive type vars. See pos/t6367 and pos/t6499 for the
competing test cases.