[GHC] #11212: Should be more liberal parsing pattern synonyms with view patterns

[GHC]

#11212: Should be more liberal parsing pattern synonyms with view patterns
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        Reporter:  mpickering        |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
  (Parser)                           |             Keywords:
      Resolution:                    |  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 thomie):

 With `-XMultiWayIf`, `if | Just True <- Just True -> True` is a valid
 expression. It looks similar to the example in this ticket: two arrows in
 opposite directions, no parenthesis.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11212#comment:3>
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