GHC panic (TypeInType)

{-# Language TypeInType, TypeFamilies, TypeOperators #-}

import Data.Kind

type a ~>> b = (a, b) -> Type

data family Sing (a::k)

type family
  (·) (f::a~>>b) (x::a)::b

class PCategory kat where
  type Id  ::kat·a·a
  type Comp::kat·b·c -> kat·a·b -> kat·a·c

class SCategory kat where
  sId   :: Sing a -> Sing (Id::kat a a)
  sComp :: Sing f -> Sing g -> Sing (Comp f g)

triggers a panic

$ ghci -ignore-dot-ghci Bug.hs
GHCi, version 8.3.20171122: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Bug.hs, interpreted )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.3.20171122 for x86_64-unknown-linux):
	piResultTy
  k_a1KI[tau:1]
  a_a1vb[sk:1]
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1147:37 in ghc:Outputable
        pprPanic, called at compiler/types/Type.hs:951:35 in ghc:Type
        piResultTy, called at compiler/types/Type.hs:2309:34 in ghc:Type
        typeKind, called at compiler/types/Type.hs:2309:46 in ghc:Type
        typeKind, called at compiler/typecheck/TcType.hs:1706:11 in ghc:TcType

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

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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