[Haskell-cafe] MonadPlus instance for IO

[David Roundy]

I'm sure I'm doing something stupid, but somehow ghc isn't recognizing the
existance of a MonadPlus instance for IO:

DarcsIO.lhs:48:
    No instance for (MonadPlus IO)
      arising from use of `mplus' at DarcsIO.lhs:48
    In the definition of `foo':
        foo = (fail "aaack") `mplus` (fail "foobar")

Any idea what I'm doing wrong? I'm using

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.2.2

packaged for debian.
-- 
David Roundy
http://www.darcs.net