[GHC] #13877: GHC panic: No skolem info: k2

[GHC]

#13877: GHC panic: No skolem info: k2
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         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 RyanGlScott):

 Going back to the original program, if you change this line:

 {{{#!hs
 listElimTyFun = listElimPoly @(:->) @a @p @l
 }}}

 To this:

 {{{#!hs
 listElimTyFun = listElimPoly @(:->)
 }}}

 You get a different panic:

 {{{
 $ /opt/ghc/8.2.1/bin/ghci Bug.hs
 GHCi, version 8.2.0.20170623: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Eliminator       ( Bug.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.0.20170623 for x86_64-unknown-linux):
         piResultTy
   Fun [a_a5hm[sk:2]] (':->) *
   l_a5ho[sk:2]
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:948:35 in ghc:Type

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13877#comment:2>
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