[GHC] #13295: Failure to resolve type parameter determined by type family

[GHC]

#13295: Failure to resolve type parameter determined by type family
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        Reporter:  alexvieth         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
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 alexvieth):

 I see. So the necessary theoretical work just hasn't been done. I hope
 that eventually `introG` can be accepted, but in the mean-time, perhaps we
 could come up with a more helpful error message?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13295#comment:3>
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