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

[Simon Peyton-Jones]

I think GHC is right here. See
http://haskell.org/onlinereport/decls.html#instance-decls
esp the bit starting "It is illegal to give a binding..."

Simon


| -----Original Message-----
| From: haskell-cafe-bounces at haskell.org [mailto:haskell-cafe-bounces at haskell.org] On Behalf Of Neil
| Mitchell
| Sent: 06 July 2008 00:03
| To: Haskell Cafe
| Subject: [Haskell-cafe] Re: Definition of hidden instance members (bug in GHC or Hugs+Yhc)
|
| >  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)
|
| Thanks
|
| Neil
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