[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):

 OK, well `monad-control` and `lifted-base` are living (very) dangerously.
 I make no claims whatever about GHC's support for impredicativity.  Might
 be worth talking to the maintainers about fixing that; it's usually a
 question of adding some newtype wrappers.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9569#comment:8>
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