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

13 Dec 2015


      #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
           Keywords:                 |  Operating System:  Unknown/Multiple
  PatternSynonyms                    |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Redundant parentheses are required around a view pattern if it is used on
 the RHS of a pattern synonym definition. I think that parsing should be
 relaxed to allow the first definition.

 {{{
 -- Fails to parse, bug?
 pattern IsTrue :: Show a => a
 pattern IsTrue <- (== "True") . show -> True

 -- Parses
 pattern IsTrue :: Show a => a
 pattern IsTrue <- ((== "True") . show -> True)
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11212
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