[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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Changes (by simonpj):

 * cc: dimitris@…, sweirich@…, eir@… (added)


Comment:

 If we promote existentials, people will want to pattern match on them to
 take them apart; we will need to deal with skolem-escape checks; etc. I
 don't know what the consequences are.  I'd be happy to be told they are
 fine, but for now the implementation definitely isn't up to it, so better
 to exclude them now and allow them later.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7347#comment:2>
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