[GHC] #14777: panic when using a function defined in terms of `error`

[GHC]

#14777: panic when using a function defined in terms of `error`
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        Reporter:  zilinc            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by zilinc):

 For quite a few times, after I change some code, if it crashes, I can
 always fix it by changing one `__impossible` to `undefined` or v.v. I'm
 unsure whether it's a coincidence or not.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14777#comment:10>
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