[GHC] #10426: matchGroupArity panic with PatternSynonyms

[GHC]

#10426: matchGroupArity panic with PatternSynonyms
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.1
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
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 Ben Gamari <ben@…>):

 In [changeset:"fdb08e2abccf1e02dc2ef91531aebe062d8af82d/ghc" fdb08e2/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="fdb08e2abccf1e02dc2ef91531aebe062d8af82d"
 Add testcase for #10426
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10426#comment:2>
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