[GHC] #9981: Potential typechecker regression in GHC 7.10.1RC

[GHC]

#9981: Potential typechecker regression in GHC 7.10.1RC
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        Reporter:  hvr               |                   Owner:  simonpj
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.1
       Component:  Compiler (Type    |                 Version:  7.10.1-rc1
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:                    |
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Comment (by simonpj):

 This definitely should not work; it requires impredicative polymoprhism
 which GHC does not properly support.

 The error message is bad, and I'll try to fix that, but I don't think it's
 urgent for 7.10.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9981#comment:3>
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