[GHC] #10732: Legal Bang Patterns cannot parse

[GHC]

#10732: Legal Bang Patterns cannot parse
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              Reporter:  rem         |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.8.3
  (Parser)                           |
              Keywords:  Bang        |  Operating System:  Unknown/Multiple
  Pattern Parser                     |
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 According to the syntax provided by GHC user guide

 pat ::= !pat

 Both !!pat and pat : !pat should be accepted, but GHC gives parsing error.
 For detail see http://stackoverflow.com/questions/31790327/where-can-
 bangpatterns-appear

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10732>
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