{-# Language KindSignatures #-}
{-# Language PolyKinds      #-}

import Data.Kind

data A n (a :: n) :: a -> Type

causes a panic on 8.7.20181017

$ ~/code/headghc/inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci 665_bug.hs
GHCi, version 8.7.20181017: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( 665_bug.hs, interpreted )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.7.20181017 for x86_64-unknown-linux):
	ASSERT failed!
  Type-correct unfilled coercion hole {co_a1xR}
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable
        pprPanic, called at compiler/utils/Outputable.hs:1219:5 in ghc:Outputable
        assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:1805:99 in ghc:TcHsSyn

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

>

and an assertion failure in 8.7.20181029

$ ~/code/unmodifiedghc/inplace/bin/ghc-stage2 --interactive -ignore-dot-ghci 665_bug.hs
GHCi, version 8.7.20181029: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( 665_bug.hs, interpreted )
*** Exception: ASSERT failed! file compiler/types/TyCon.hs, line 420
>