[GHC] #8632: ghc: panic! (the 'impossible' happened)

[GHC]

#8632: ghc: panic! (the 'impossible' happened)
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       Reporter:  jdoliner        |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler        |           Version:  7.4.1
       Keywords:                  |  Operating System:  Unknown/Multiple
   Architecture:  x86_64 (amd64)  |   Type of failure:  Compile-time crash
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 I got this message when trying to compile. It appears to be reproducible.
 Also I realize this is an outdate version of GHC so I'm going to update
 and see if it fixes itself.

   (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,
                                                         _)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8632>
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