Assertion failure in demand analyser with levity polymorphic code

Steps to reproduce

Compile the following code with -O (extracted from the unboxed library)

{-# Language DataKinds #-}
{-# Language NoImplicitPrelude #-}
{-# Language RebindableSyntax #-}

module Def.Int where

import GHC.Types
import qualified Prelude

class Eq (a :: TYPE r) where
  (==) :: a -> a -> Bool

class Num (a :: TYPE r) where
  fromInteger :: Prelude.Integer -> a

roundDef :: forall (a :: TYPE IntRep) . (Eq a, Num a) => a -> ()
roundDef 0 = ()

This results in

ghc: panic! (the 'impossible' happened)
  GHC version 9.3.20210519:
	ASSERT failed!
  ($dNum_aDR
   `cast` (N:Num[0] <'IntRep>_N <a_aDP>_N
           :: Num a_aDP ~R# (Integer -> a_aDP)))
    lvl_sEX
  Call stack:
      CallStack (from HasCallStack):
        assertPpr, called at compiler/GHC/Core/Opt/DmdAnal.hs:345:5 in ghc:GHC.Core.Opt.DmdAnal
        dmdAnalStar, called at compiler/GHC/Core/Opt/DmdAnal.hs:391:29 in ghc:GHC.Core.Opt.DmdAnal

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

Environment

• GHC version used: HEAD (9.3.20210519)