haskell/haskell-mode — pull request #54 by mstrlu (2012-06-03 08:23:03+00:00)
Title: Don't replace buffer when stylish-haskell fails.

I just opened a file I was working on yesterday and it only contained:
```
stylish-haskell: StylishHaskell.Parse.parseModule: could not parse : ParseFailed (SrcLoc {srcFilename = ".hs", srcLine = 34, srcColumn = 9}) "Parse error: ="
```
so I suppose something like this fix is needed.