[GHC] #6032: HEAD (7.5.20120421) requires RankNTypes for a rank-2 type

[GHC]

#6032: HEAD (7.5.20120421) requires RankNTypes for a rank-2 type
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    Reporter:  dreixel           |       Owner:  simonpj         
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:  7.8.1           
   Component:  Compiler          |     Version:  7.5             
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by illissius):

 Might the reason for the separation have been that type inference is in
 theory decidable for rank-2 types, but not higher? I'm not a type theorist
 but I found this for example:
 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.144.1202
 (WRT the deprecation/aliasing proposal itself I don't have an opinion)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6032#comment:7>
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