[GHC] #12700: Don't warn about redundant constraints for type equalities

[GHC]

#12700: Don't warn about redundant constraints for type equalities
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        Reporter:  crockeea          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by hsyl20):

 * cc: hsyl20 (added)


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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12700#comment:5>
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