[GHC] #12108: Function type synonym fails in pattern synonym

23 May 2016


      #12108: Function type synonym fails in pattern synonym
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  PatternSynonyms                    |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  11977
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 pattern Id :: a -> a
 pattern Id x = x
 }}}

 works but

 {{{#!hs
 -- • Pattern synonym ‘Id’ has one argument
 --     but its type signature has none
 -- • In the declaration for pattern synonym ‘Id’
 type Endo a = a -> a

 pattern Id :: Endo a
 pattern Id x = x
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12108
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