[GHC] #13787: The compiler told me to report this. I have no idea what happened

[GHC]

#13787: The compiler told me to report this. I have no idea what happened
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        Reporter:  gleb_dianov       |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:  duplicate         |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13106            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by gleb_dianov):

 Replying to [comment:3 RyanGlScott]:
 > Thanks for the bug report. I don't have time to dig into the internals
 of your particular project, but there is a 99.9% chance that this is an
 occurrence of #13106, a known bug which has been fixed in GHC 8.2.1. The
 underlying cause is usually that you forgot to import some top-level
 identifier (in your case, probably `err`).

 This error didn't occur after I fixed some compile-time errors in the
 module (didn't have any problems with imports though), so I'm happy

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13787#comment:4>
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