[GHC] #15597: GHC shouting: panic!

[GHC]

#15597: GHC shouting: panic!
-------------------------------------+-------------------------------------
           Reporter:  tstr           |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.4.1
           Keywords:  TypeInType     |  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:
-------------------------------------+-------------------------------------
 This program makes the impossible happen:

 {{{#!hs
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TypeInType #-}

 import GHC.Types

 data Bug :: (f x -> Type) -> Type where
   Bug :: forall
    (r::h -> forall x. f x -> Type)
    (a::f x)
    .  (r::((f x -> Type) -> Type) -> forall x. f x -> Type) Bug a
    -> Bug (r::f x -> Type)
 }}}


 And asked for reporting the error:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.4.1 for x86_64-unknown-linux):
         piResultTy
   k_aozeA[tau:1]
   (x_aozeN[sk:2] |> {co_aozeO})
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:950:35 in ghc:Type
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15597>
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