[GHC] #10339: PatternSynonyms confuse exhaustiveness check

[GHC]

#10339: PatternSynonyms confuse exhaustiveness check
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        Reporter:  hvr               |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.1
      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 Revisions:
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Changes (by hvr):

 * version:  7.10.1 => 7.8.1


Comment:

 This occurs since GHC 7.8 (when pattern synonyms were introduced), up to
 GHC HEAD

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10339#comment:1>
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