[GHC] #2993: Precedence errors are reported for undefined operators

[GHC]

#2993: Precedence errors are reported for undefined operators
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Reporter:  Olathe            |          Owner:                  
    Type:  feature request   |         Status:  new             
Priority:  normal            |      Component:  Compiler        
 Version:  6.10.1            |       Severity:  normal          
Keywords:                    |       Testcase:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
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 I found a misleading error message.

 If I add the import for (<$>), but I forget to save the file
 {{{
 -- other imports
 -- import Control.Applicative ((<$>))
 main = print $ (+1).(+2) <$> Just 5
 }}}
 I get the error
 {{{
     precedence parsing error
         cannot mix `(.)' [infixr 9] and `(<$>)' [infixl 9] in the same
 infix expression
 }}}
 which is rather hard to debug, since it makes it seem that the problem is
 either with Control.Applicative's precedence definitions or that I've
 somehow imported (<$>) with a different precedence from somewhere else.

 It would be nice if it would report instead that (<$>) wasn't defined yet.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2993>
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