[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:  danharaj
            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:  #5835             |  Differential Rev(s):  Phab:D2714
       Wiki Page:                    |
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Comment (by rwbarton):

 Another potential instance of this spotted in the wild: `MonadBaseControl
 IO m => m ()`, where `MonadBaseControl b m` has indirect superclasses
 including `Applicative b` and `Monad b`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12791#comment:29>
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