[GHC] #10011: The Data instance for Ratio violates internal invariants.

[GHC]

#10011: The Data instance for Ratio violates internal invariants.
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        Reporter:  ekmett            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.10.1
       Component:  Core Libraries    |                 Version:  7.10.1-rc1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D625
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Comment (by simonpj):

 By all means go ahead and add the test, but it'd be good to include
 comments that articulate what exactly it is testing!

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10011#comment:14>
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