mozilla/rust — pull request #11662 by alexcrichton (2014-01-19 08:02:02+00:00)
Title: Fix a pathological const checking case

The included test case would essentially never finish compiling without this
patch. It recursies twice at every ExprParen meaning that the branching factor
is 2^n

The included test case will take so long to parse on the old compiler that it'll
surely never let this crop up again.