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On GHC 9.4 and HEAD, the following program causes a panic:

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE StandaloneKindSignatures #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UnliftedNewtypes #-}

module T21544 where

import Data.Kind
import GHC.Exts

type N :: forall (r :: RuntimeRep) -> TYPE r -> TYPE r
data family N r a
newtype instance N r a = MkN a

foo :: Int# -> N IntRep Int#
foo = MkN

<no location info>: error:
    panic! (the 'impossible' happened)
  GHC version 9.5.20220503:
        isUnliftedType
  a_aXy :: TYPE r_aXx
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler\GHC\Utils\Panic.hs:182:37 in ghc:GHC.Utils.Panic
        pprPanic, called at compiler\GHC\Core\Type.hs:2484:7 in ghc:GHC.Core.Type
        isUnliftedType, called at compiler\GHC\Core\Opt\Simplify.hs:2900:5 in ghc:GHC.Core.Opt.Simplify

The program seems to be OK on GHC 9.2 and below.