[GHC] #9210: "overlapping instances" through FunctionalDependencies

[GHC]

#9210: "overlapping instances" through FunctionalDependencies
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        Reporter:  rwbarton          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.8.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 Somehow, this program no longer compiles in GHC 8.0 or HEAD. Yay!

 I'd rather not just close this without knowing why it was fixed, and we
 should add a regression test.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9210#comment:5>
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