panic validHoleFits no evdest

Summary

I was playing around with two-level free monads and encountered a panic for this program:

{-# LANGUAGE GADTs #-}
{-# LANGUAGE QuantifiedConstraints #-}

module Panic where

import Control.Monad
import Data.Type.Equality
import Data.Kind

type Name :: Type -> Type
newtype Name a = Name Int

newtype TL f g a = TL { unTL :: Freer f (FreerS g a) }
instance Functor (TL f g) where
instance Applicative (TL f g) where
instance Monad (TL f g) where

data Freer f a = Pure a | forall x. Freer (f x) (x -> Freer f a)
instance Functor (Freer f) where
instance Applicative (Freer f) where
instance Monad (Freer f) where

data FreerS f a = PureS a | forall x. FreerS (f (Name x)) (Name x) (FreerS f a)

instance Functor (FreerS f) where
instance Applicative (FreerS f) where
instance Monad (FreerS f) where

class Alpha a where
  rename :: Name b -> Name b -> a -> a

data (f + g) x = L (f x) | R (g x)

data Count a where
  Incr :: Count ()

handleM 
  :: forall a b h g f t. (Alpha a, forall x. Alpha (g x), forall x. Alpha (f x))
  => (forall x. g x -> h x)
  -> (a -> TL t h b)
  -> (forall x. f (Name x) -> (Name x -> TL t h b) -> TL t h b)
  -> TL t (f + g) a
  -> TL t h b
handleM sub gen alg = flush >=> go where
  go :: FreerS (f + g) a -> TL t h b
  go (PureS x) = gen x
  go (FreerS op n k) =
    case op of
      L op' -> alg op' (\n' -> go (rename n n' k))
      R op' -> hoist (FreerS (sub op') n) (go k)

flush :: TL f g a -> TL f g' (FreerS g a)
flush (TL m) = TL (fmap pure m)

count :: TL (Count + f) g a -> TL f g (Int, a)
count = handleM id (raise . fmap (0,)) $ \op k ->
  case op of
    Incr -> k _

I know there's a bug in this program in that I wanted to use another handleC function instead of handleM in count, but I didn't expect the panic:

<no location info>: error:
    panic! (the 'impossible' happened)
  GHC version 9.4.4:
	validHoleFits no evdest
  [G] Name x_a1bc[sk:2] ~# ()
  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/Tc/Errors.hs:1459:22 in ghc:GHC.Tc.Errors

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

Environment

• GHC version used: 9.4.4