[Haskell-cafe] Re: Definition of hidden instance members (bug in GHC or Hugs+Yhc)

Neil Mitchell ndmitchell at gmail.com
Sat Jul 5 19:02:52 EDT 2008

>  This is either a GHC bug, or a Yhc+Hugs bug - I'm not sure which, but
>  the compilers disagree:
>  import Prelude hiding ((==))
>  data Foo = Foo
>  instance Eq Foo where
>     (==) a b = True

I was thinking that GHC's behaviour seems more sensible, but the
following fails:

import qualified Module as M

instance MClass Foo where
     M.foo = undefined

M. is not allowed as a prefix of a function, which makes resolving
ambiguities hard unless the compiler solves the issue for you (as Hugs
and Yhc do)



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