[GHC] #12791: Superclass methods could be more aggressively specialised.

[GHC]

#12791: Superclass methods could be more aggressively specialised.
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        Reporter:  mpickering        |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 Yes and here is another example from transformers.

 {{{#!hs
 class (Monoid w, Monad m) => MonadWriter w m | m -> w where
 }}}

 It is suggested to write functions of the form,

 {{{#!hs
 f :: (MonadWriter MyMonoid m) => m ....
 }}}

 which will have the same problem.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12791#comment:13>
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