[GHC] #13546: Kind error with type equality

[GHC]

#13546: Kind error with type equality
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        Reporter:  int-index         |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:  invalid           |             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 int-index):

 Yes, the difference between `C a a` and `a~b => C a b` is what I meant.
 Thank you for explanations, very helpful!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13546#comment:8>
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