[GHC] #11213: Incorrect reported pattern synonym signature

13 Dec 2015

      #11213: Incorrect reported pattern synonym signature
-------------------------------------+-------------------------------------
           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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 {{{
 data T where
   MkT :: (Show b) => b -> T

 --pattern ExNumPat :: () => Show b => b -> T
 pattern ExNumPat x = MkT x
 }}}

 GHC reports that `ExNumPat` is missing a signature (correctly) but it
 reports the wrong type. The correct type is the one commented out.

 {{{
 pstest.hs:12:1: warning:
     Top-level binding with no type signature:
       ExNumPat :: forall b. Show b => b -> T
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11213
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