[GHC] #12730: Pattern synonym signature fails with unlifted type

17 Oct 2016


      #12730: Pattern synonym signature fails with unlifted type
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           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           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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 {{{#!hs
 pattern P2# a b = (# a, b #)
 }}}

 works but adding a type signture makes it fail

 {{{#!hs
 -- tp0w.hs:130:25-34: error: …
 --     • Expecting a lifted type, but ‘(# a, b #)’ is unlifted
 --     • In the type ‘(# a, b #)’
 -- Compilation failed.
 pattern P2# :: a -> b -> (# a, b #)
 pattern P2# a b = (# a, b #)
 }}}

 Same with these

 {{{#!hs
 pattern True :: Int#
 pattern True = 1#

 pattern False :: Int#
 pattern False = 0#
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12730
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