[GHC] #9092: ghc: panic! (the 'impossible' happened)

[GHC]

#9092: ghc: panic! (the 'impossible' happened)
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       Reporter:  alex404          |             Owner:
           Type:  bug              |            Status:  new
       Priority:  normal           |         Milestone:
      Component:  Compiler         |           Version:  7.8.2
       Keywords:  panic            |  Operating System:  Linux
  impossible                       |   Type of failure:  Compile-time crash
   Architecture:                   |         Test Case:
  Unknown/Multiple                 |          Blocking:
     Difficulty:  Unknown          |
     Blocked By:                   |
Related Tickets:                   |
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 I'm not sure *why* this is happening, but I know where. The code for this
 library is available here: http://hub.darcs.net/alex404/hsl-random

 So as is, I can run the script called multivariate and get the expected
 results, but when I try to compile I get

 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.2 for x86_64-unknown-linux):
         attempt to prod-split usage call demand C(C1(U(U,U,U,U,U,U)))

 If at line 317 in Scientific.Random.Distributions.hs, I replace the
 statement sgma = ... with sgma = undefined, the code will compile, though
 obviously it cannot be used. If I transform the code in other ways which
 are meant to preserve the results, I can get it to compile, but then the
 script hangs.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9092>
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