Commit 2b670a79 authored by Simon Marlow's avatar Simon Marlow
Browse files

disable MonadPlus instance that doesn't compile with 6.6

parent 904addb8
......@@ -139,9 +139,15 @@ unsafeInterleaveM (IOEnv m) = IOEnv (\ env -> unsafeInterleaveIO (m env))
-- For use if the user has imported Control.Monad.Error from MTL
-- Requires UndecidableInstances
#if __GLASGOW_HASKELL__ > 606
-- for some reason, this doesn't compile with GHC 6.6:
-- utils/IOEnv.hs:144:33:
-- No instance for (MonadPlus IO)
-- arising from use of `mplus' at utils/IOEnv.hs:144:33-67
instance MonadPlus IO => MonadPlus (IOEnv env) where
mzero = IOEnv (const mzero)
m `mplus` n = IOEnv (\env -> unIOEnv m env `mplus` unIOEnv n env)
#endif
----------------------------------------------------------------------
-- Accessing input/output
......
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