[GHC] #6008: ghc: panic! (the 'impossible' happened)

[GHC]

#6008: ghc: panic! (the 'impossible' happened)
--------------------------+-------------------------------------------------
 Reporter:  jtb           |          Owner:                
     Type:  bug           |         Status:  new           
 Priority:  normal        |      Component:  Compiler      
  Version:  7.4.1         |       Keywords:                
       Os:  Linux         |   Architecture:  x86_64 (amd64)
  Failure:  None/Unknown  |       Testcase:                
Blockedby:                |       Blocking:                
  Related:                |  
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Comment(by michalt):

 Thanks for reporting! This seems to be fixed in HEAD :)
 {{{
 > ~/dev/ghc-clean/inplace/bin/ghc-stage2 -O2 -fforce-recomp -rtsopts
 keltis_typedefs.hs
 [1 of 1] Compiling Main             ( keltis_typedefs.hs,
 keltis_typedefs.o )

 keltis_typedefs.hs:6:29:
     Illegal deriving item `eq'
     In the data declaration for `PlayingCard'

 keltis_typedefs.hs:13:24:
     Illegal deriving item `eq'
     In the data declaration for `Colour'

 keltis_typedefs.hs:16:29:
     Illegal deriving item `eq'
     In the data declaration for `PlayersHand'
 }}}
 but not in the 7.4 branch. I'm not closing since I'm not sure which commit
 did
 actually fix this and if it is easy to merge it into 7.4 branch (from
 briefly
 looking at the logs it might have been
 3bf54e78cfd4b94756e3f21c00ae187f80c3341d).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6008#comment:2>
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