[GHC] #7901: Bad error message when using UnicodeSyntax ∀ without ExplicitForall

9 May 2013


      #7901: Bad error message when using UnicodeSyntax ∀ without ExplicitForall
----------------------------------------------+-----------------------------
Reporter:  exbb2                              |          Owner:                  
    Type:  bug                                |         Status:  new             
Priority:  normal                             |      Component:  Compiler        
 Version:  7.6.2                              |       Keywords:                  
      Os:  Unknown/Multiple                   |   Architecture:  Unknown/Multiple
 Failure:  Incorrect warning at compile-time  |      Blockedby:                  
Blocking:                                     |        Related:                  
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 This code
 {{{
 {-# LANGUAGE UnicodeSyntax #-}

 id' :: ∀ a. a → a
 id' a = a
 }}}
 produces following error
 {{{
 /tmp/id.hs:4:8: parse error on input `∀'
 }}}
 However, equivalent code without unicode syntax gives a much better error
 message:
 {{{
 id' :: forall a. a → a
 id' a = a
 }}}
 {{{
 /tmp/id.hs:4:16:
     Illegal symbol '.' in type
     Perhaps you intended -XRankNTypes or similar flag
     to enable explicit-forall syntax: forall <tvs>. <type>
 }}}

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7901
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