[GHC] #10855: GHC rejects code that Haskell 2010 report accepts

8 Sep 2015

      #10855: GHC rejects code that Haskell 2010 report accepts
-------------------------------------+-------------------------------------
              Reporter:  goldfire    |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 According to
 [https://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-220003
 The Haskell 2010 Report], the following two modules should compile. But
 they don't, failing with parse errors:

 {{{
 {-# LANGUAGE Haskell2010 #-}

 module Bug where

 bool = - case b of False -> 0; True -> (-1)
 }}}

 {{{
 {-# LANGUAGE Haskell2010 #-}

 instance Num (IO a) where
   negate = id

 main = - do putStrLn "hi!"
 }}}

 Note the unary `-` signs.

 I'm not sure whether we should complicate the parser to fix these, but we
 should document the compliance-failure in the manual.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10855
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