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

[GHC]

#7066: isInstance does not work for compound types
------------------------------+---------------------------------------------
 Reporter:  edsko             |          Owner:                  
     Type:  bug               |         Status:  new             
 Priority:  normal            |      Component:  Template Haskell
  Version:  7.4.2             |       Keywords:                  
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  None/Unknown      |       Testcase:                  
Blockedby:                    |       Blocking:                  
  Related:                    |  
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 Consider

 {{{
 import Language.Haskell.TH.Syntax

 data A = A

 test :: Q [Dec]
 test = do
   tp <- [t| (Int, A) |]
   inst1 <- isInstance ''Show [ tp ]
   runIO $ print inst1
   return []
 }}}

 This prints True even though there is no Show instance for A (the Show
 instance it finds is for pairs, but it does not verify that there are Show
 instances for the pair components).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7066>
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