[GHC] #11977: ghc doesn't agree with its own inferred pattern type

[GHC]

#11977: ghc doesn't agree with its own inferred pattern type
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 GHCi, version 8.1.20160419:

 {{{
 pattern F a <- (($ 'a') -> a)
 }}}

 {{{
 >>> :i F
 pattern F :: b -> Char -> b     -- Defined at /tmp/tTaa.hs:24:1
 }}}

 Putting them together:

 {{{
 -- tTaa.hs:25:9: error: …
 --     • Pattern synonym ‘F’ has one argument
 --         but its type signature has two
 --     • In the declaration for pattern synonym ‘F’
 Compilation failed.
 pattern F :: b -> Char -> b
 pattern F a <- (($ 'a') -> a)
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11977>
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