[GHC] #708: Compiler error

[GHC]

#708: Compiler error
--------------------------------------------+-------------------------------
  Reporter:  r.j.rorije at student.utwente.nl  |          Owner:         
      Type:  bug                            |         Status:  new    
  Priority:  normal                         |      Milestone:         
 Component:  Compiler                       |        Version:  6.4.1  
  Severity:  normal                         |     Resolution:         
  Keywords:                                 |             Os:  Windows
Difficulty:  Unknown                        |   Architecture:  x86    
--------------------------------------------+-------------------------------
Changes (by r.j.rorije at student.utwente.nl):

  * summary:  Error: Data.Generics / Cast => Compiler error

Comment:

 Hi,

 Ralf Lammel simplified the test case considerably, even without using
 Data.Generics or cast, so I do not know where the error comes from
 anymore, but it should limit the search area.


 {{{
 module Test where

   class C a where
     mycast :: (C b) => a -> Maybe b
     mycast = undefined
     equals :: (C b) => a -> b -> Bool
     equals = undefined

   instance C Int

   data T1 = N11 Int

   instance C T1 where
     mycast (N11 x) = undefined
     x `equals` y = (mycast x :: Maybe Int) == undefined
   {-
   *Test> N11 5 `equals` N11 5
   : panic! (the `impossible' happened, GHC version 6.4.1):
           nameModule mycast{v a1Gt}
   -}
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/708>
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