[GHC] #890: ghc panics on accessing a labeled field

[GHC]

#890: ghc panics on accessing a labeled field
-------------------------+--------------------------------------------------
    Reporter:  guest     |        Owner:         
        Type:  bug       |       Status:  new    
    Priority:  normal    |    Milestone:         
   Component:  Compiler  |      Version:  6.4.2  
    Severity:  normal    |     Keywords:         
          Os:  Windows   |   Difficulty:  Unknown
Architecture:  x86       |  
-------------------------+--------------------------------------------------
GHC panics about a following code:
 {{{
 class Bar a where
         bar :: Foo a -> Foo a
         bar x = x { foo = [] }

 data Foo a = Bar a => Foo { foo :: [a] }
 }}}
 GHC says:

 Chasing modules from: Main.hs
 Compiling Main             ( Main.hs, Main.o )
 ghc: panic! (the `impossible' happened, GHC version 6.4.2):
         types/Type.lhs:(1107,0)-(1108,77): Non-exhaustive patterns in
 function zip_ty_env

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/890>
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