[GHC] #11367: [Regression] Only one clause allowed in (explicitly bidirectional) pattern synonyms

[GHC]

#11367: [Regression] Only one clause allowed in (explicitly bidirectional) pattern
synonyms
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
                                     |  PatternSynonyms
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 I think this reply is a mixture of a new ticket, #393 and some more
 context for this ticket.

 > Could you not view a where clause in a pattern synonym as containing
 zero bindings (unidirectional) or a single binding (explicitly
 bidirectional).

 Yes you could, without looking I think this would require quite a bit of
 refactoring because of how everything is dealt with in the parser.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11367#comment:10>
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