[GHC] #9773: Binding ImplicitParams in lambda results in parse error

5 Nov 2014


      #9773: Binding ImplicitParams in lambda results in parse error
-------------------------------------+-------------------------------------
       Reporter:  SimonHengel        |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler (Parser)  |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:  GHC
     Blocked By:                     |  rejects valid program
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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 {{{ImplicitParams}}} currently do not play well with lambdas :(

 == Steps to reproduce

 Create a file {{{Foo.hs}}} with the following content:

 {{{
 {-# LANGUAGE ImplicitParams #-}

 import Control.Monad

 foo :: (?bar :: Int) => IO ()
 foo = print ?bar

 main = do
   forM_ [1..3] $ \ ?bar -> foo
 }}}

 === Expected result

 {{{
 $ runhaskell Foo.hs
 1
 2
 3
 }}}

 === Actual result

 {{{
 $ runhaskell Foo.hs

 Foo.hs:9:21: Parse error in pattern: ?bar
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9773
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