[GHC] #7911: The following code makes ghc panic

15 May 2013


      #7911: The following code makes ghc panic
-----------------------------+----------------------------------------------
Reporter:  guest             |          Owner:                  
    Type:  bug               |         Status:  new             
Priority:  normal            |      Component:  Compiler        
 Version:  7.4.2             |       Keywords:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
 Failure:  None/Unknown      |      Blockedby:                  
Blocking:                    |        Related:                  
-----------------------------+----------------------------------------------
 This code has a bug (lowercase show instead of uppercase Show), but it
 shouldn't make the compiler crash.

 {{{
 {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, FlexibleContexts,
 UndecidableInstances #-}

 data Person = SnowWhite | Dwarf Int deriving (show, Eq, Ord)
 }}}

 Result:


 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.4.2 for i386-unknown-mingw32):
         nameModule show{tv avGJ}

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

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7911
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler