[GHC] #3775: Pattern matching on Word literals in GHCi crashes.

[GHC]

#3775: Pattern matching on Word literals in GHCi crashes.
-------------------------------+--------------------------------------------
    Reporter:  diatchki        |       Owner:            
        Type:  bug             |      Status:  new       
    Priority:  normal          |   Component:  GHCi      
     Version:  6.10.4          |    Keywords:            
          Os:  Linux           |    Testcase:            
Architecture:  x86_64 (amd64)  |     Failure:  GHCi crash
-------------------------------+--------------------------------------------
 GHCi 6.10.4 seems to be crashing with "impossible happened" when loading
 the program bellow.  The problem seems to be related to pattern matching
 on Word literals, as it does not seem to happen if I change Word to Int.


 {{{
 module Bug where

 import Data.Word(Word)

 bug :: Word -> Bool
 bug x = case x of
           0 -> True
           _ -> False


 }}}

 Output:
 {{{
 GHCi, version 6.10.4: http://www.haskell.org/ghc/  :? for help
 Loading package ghc-prim ... linking ... done.
 Loading package integer ... linking ... done.
 Loading package base ... linking ... done.
 [1 of 1] Compiling Bug              ( Bug.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 6.10.4 for x86_64-unknown-linux):
         schemeE(AnnCase).my_discr __word 0

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 -Iavor

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3775>
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