[GHC] #9569: Tuple constraints don't work right

[GHC]

#9569: Tuple constraints don't work right
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              Reporter:  simonpj     |            Owner:
                  Type:  bug         |           Status:  closed
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.2
            Resolution:  fixed       |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
  polykinds/T9569,                   |
  typecheck/should_compile/T9569a    |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Bas, I'm not sure.   I don't see anything impredicative about `Run`, just
 higher rank.  Moreover, I see no mention of `-XImpredicativeTypes` in the
 LANGUAGE extensions or cabal file.

 So I'm confused.  What's the problem here?

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9569#comment:12>
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