[GHC] #5462: Deriving clause for arbitrary classes

[GHC]

#5462: Deriving clause for arbitrary classes
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    Reporter:  simonpj           |        Owner:              
        Type:  feature request   |       Status:  new         
    Priority:  normal            |    Milestone:              
   Component:  Compiler          |      Version:  7.2.1       
    Keywords:                    |     Testcase:              
   Blockedby:                    |   Difficulty:              
          Os:  Unknown/Multiple  |     Blocking:              
Architecture:  Unknown/Multiple  |      Failure:  None/Unknown
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Comment(by simonpj):

 I hate the `{-# DERIVABLE C #-}` pragma though -- it's not really a pragma
 at all (in the sense of affecting optimisation but not semantics or what
 programs are typeable).  But we need ''some'' way to say that class C is
 one that can appear in a deriving clause.  We can't allow just any old
 class in a deriving clause!

 Any other ideas?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5462#comment:6>
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