[GHC] #5333: Arrow command combinators and infixr cause the desugarer to fail

[GHC]

#5333: Arrow command combinators and infixr cause the desugarer to fail
---------------------------------+------------------------------------------
    Reporter:  peteg             |       Owner:                           
        Type:  bug               |      Status:  new                      
    Priority:  normal            |   Component:  Compiler (Parser)        
     Version:  7.0.3             |    Keywords:                           
    Testcase:                    |   Blockedby:                           
          Os:  Unknown/Multiple  |    Blocking:                           
Architecture:  Unknown/Multiple  |     Failure:  GHC rejects valid program
---------------------------------+------------------------------------------
 The following code exhibits the bug:

 {{{
 {-# LANGUAGE Arrows, NoMonomorphismRestriction #-}
 module T where

 import Prelude hiding ( id, (.) )
 import Control.Arrow

 cc1 :: Arrow a => a e b -> a e b -> a e b
 cc1 = undefined

 -- 'g' fails to compile.
 -- g = proc (x, y, z) ->
 --   ((returnA -< x) &&& (returnA -< y) &&& (returnA -< z))

 -- 'f' compiles:
 --   - without an infix declaration
 --   - with the infixl declaration
 -- and fails with the infixr declaration
 infixr 6 `cc1`
 -- infixl 6 `cc1`

 f = proc (x, y, z) ->
   ((returnA -< x) `cc1` (returnA -< y) `cc1` (returnA -< z))

 }}}

 GHC says:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.0.3 for i386-apple-darwin):
         dsSyntaxTable Not found: base:GHC.Desugar.>>>{v 01W}
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5333>
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