[GHC] #8169: ghc: panic! (the 'impossible' happened)

[GHC]

#8169: ghc: panic! (the 'impossible' happened)
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       Reporter:  guest           |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler        |           Version:  7.4.1
       Keywords:                  |  Operating System:  Linux
   Architecture:  x86_64 (amd64)  |   Type of failure:  None/Unknown
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 ghc: panic! (the 'impossible' happened)
   (GHC version 7.4.1 for x86_64-unknown-linux):
         compiler/rename/RnSource.lhs:429:14-81: Irrefutable pattern failed
 for pattern Data.Maybe.Just (inst_tyvars,
                                                         _,
                                                         SrcLoc.L _ cls,
                                                         _)


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


 --------------------------
 The message  appeared after inserting

 data CSeq a = CSeq [a]
 instance (context => CDelimeter) CProd CSeq a where
     produce context (CSeq x) = map (produce context) x

 ghc is from standard ubuntu package.
 >> haskell-compiler --version
 The Glorious Glasgow Haskell Compilation System, version 7.4.1

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8169>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler