[GHC] #13547: ghc: panic! StgCmmEnv: variable not found

[GHC]

#13547: ghc: panic! StgCmmEnv: variable not found
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        Reporter:  cipher1024        |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  10158             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by cipher1024):

 Yeah, the parser is fairly complex. Thank you for trying to minimize it
 yourself.

 So here's a game plan:
 0. minimize the example
 1. get / build ghc HEAD
 2. try it on example.

 I have never worked on ghc. What is the simplest way to get ghc HEAD to
 test my example with it?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13547#comment:8>
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