[GHC] #7066: isInstance does not work for compound types

[GHC]

#7066: isInstance does not work for compound types
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    Reporter:  edsko             |       Owner:  simonpj         
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Template Haskell  |     Version:  7.4.2           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by edsko):

 I see. Fair enough, but then it would be very useful if a separate
 function was provided that ''does'' have the "expected" behaviour for
 things like (Int, A) (for some definition of "expected" :). It's not
 obvious to me that such a function is easily user-definable.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7066#comment:2>
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