[Haskell-cafe] Noticed this change about infix decls in GHC 7.4.2

[Simon Peyton-Jones]

Yes, it's a bug.  Happily a dup of http://hackage.haskell.org/trac/ghc/ticket/6120, which is already fixed. I'll add your program as a regression test though.

Thanks for reporting

Simon

|  -----Original Message-----
|  From: haskell-cafe-bounces at haskell.org [mailto:haskell-cafe-
|  bounces at haskell.org] On Behalf Of Christopher Done
|  Sent: 17 June 2012 19:54
|  To: Haskell Cafe
|  Subject: [Haskell-cafe] Noticed this change about infix decls in GHC 7.4.2
|  
|  So I have some module, in a work project that I'm portnig from GHC
|  6.12.3 to GHC 7.4.2,
|  
|  module Data.Monoid.Operator where
|  
|  import Data.Monoid
|  
|  (++) :: Monoid a => a -> a -> a
|  (++) = mappend
|  infixr 5 ++
|  
|  This compiles happily on GHC 6.12.3, but on 7.4.2 says:
|  
|  src/Data/Monoid/Operator.hs:9:10:
|      Ambiguous occurrence `++'
|      It could refer to either `Data.Monoid.Operator.++',
|                               defined at src/Data/Monoid/Operator.hs:8:1
|                            or `Prelude.++',
|                               imported from `Prelude' at
|  src/Data/Monoid/Operator.hs:3:8-27
|                               (and originally defined in `GHC.Base')
|  
|  It seems that it used to assign higher priority to the declared thing
|  in the current module over the imported one. Is this intentional? I'd
|  suspect not, given that if I comment the binding out:
|  
|  -- (++) :: Monoid a => a -> a -> a
|  -- (++) = mappend
|  
|  I get:
|  
|  src/Data/Monoid/Operator.hs:9:10:
|      The fixity signature for `++' lacks an accompanying binding
|        (The fixity signature must be given where `++' is declared)
|  
|  Which seems to contradict the previous error message.
|  
|  Bug?
|  
|  Ciao!
|  
|  P.S. Yes, I know I can fix this by not importing Prelude.
|  P.P.S Yes, I know there's a <> or <+> defined now, but I prefer (++), thanks.
|  
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