[GHC] #5863: Deriving Typeable for data families

[GHC]

#5863: Deriving Typeable for data families
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    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:  7.6.2           
   Component:  Compiler          |     Version:  7.4.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonpj):

 You've convinced me to be dubious about #7897 (see comment added).  So
 yes, let's disable `deriving Typeable` for family instances, with a
 message saying that you need to derive it for the family itself.  And some
 words for the user manual would be good.  Thanks.

 Simon

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5863#comment:6>
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