[GHC] #7347: Existential data constructors should not be promoted

[GHC]

#7347: Existential data constructors should not be promoted
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    Reporter:  simonpj           |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonpj):

 As far as I know, we don't currently have a mechanism for pattern matching
 on an existential data constructor at the type level.  I'm pretty sure
 that 7.6.1 is broken in this respect.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7347#comment:4>
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