[GHC] #13931: GHC incorrectly considers type family instances conflicting?

[GHC]

#13931: GHC incorrectly considers type family instances conflicting?
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        Reporter:  vagarenko         |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  duplicate         |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11715            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 No, I meant what I said. I should have included `kx2 |-> kx1` as well,
 though.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13931#comment:5>
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