[GHC] #13674: Poor error message which masks occurs-check failure (was: GHC doesn't discharge heterogeneous equality constraint when it ought to)

[GHC]

#13674: Poor error message which masks occurs-check failure
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 > I'm inclined to say that we let this behavior stand. Note that when we
 accept the program, nothing goes wrong.

 OK, I can live with that. Sorry for derailing the discussion in the ticket
 a bit, but I wanted make sure I understood what was going on.

 Since the behavior here seems to be correct (modulo error messages), I'll
 change the title accordingly.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13674#comment:10>
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