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{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies,
ExistentialQuantification, FlexibleContexts #-}
{- Email 30 Jan 2006
> the attached program compiles under GHC, but not with Hugs. as far as
> i see, Hugs don't use dependencies in class headers to figure out that
> there is only one "vMkIOError" that can be called in the last
> definition
OK, I think it's a bug (though the example is bizarre). Sadly Hugs's
support for FDs is rough around the edges (and unlikely to improve
soon).
-}
module ShoudlCompile where
class (Monad m) => Stream m h | h->m where
vMkIOError :: h -> Int
data BinHandle = forall h . Stream IO h => BinH h
instance Stream IO BinHandle where
vMkIOError (BinH h) = vMkIOError h
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