[GHC] #15586: Compilation panic! (the 'impossible' happened)

[GHC]

#15586: Compilation panic! (the 'impossible' happened)
-------------------------------------+-------------------------------------
           Reporter:  subaruru       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
           Keywords:                 |  Operating System:  Linux
       Architecture:  x86_64         |   Type of failure:  Compile-time
  (amd64)                            |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 See attached zip for entire project causing error. I'd imagine it's pretty
 reproducible, just call stack build. I'm running standard lts-12.8 and
 it's just two small files that don't do anything yet!
 Also included is panicmessage.txt showing the exact output, crucially:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.4.3 for x86_64-unknown-linux):
         piResultTy
   *
   v_XabT
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:947:35 in ghc:Type

 }}}

 Oh and sysinfo


 {{{
 uname -a
 Linux @@@ 4.16.11-100.fc26.x86_64 #1 SMP Tue May 22 20:02:12 UTC 2018
 x86_64 x86_64 x86_64 GNU/Linux
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15586>
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