Panic with valid hole fits + unsatisiable constraint

This program causes a panic in 9.4 and master:

{-# LANGUAGE DataKinds #-}
module M where

data F x

p :: forall r p. ((r ~ Just p) => F r) -> F r
p = undefined

q :: F Nothing
q = p _

    panic! (the 'impossible' happened)
  GHC version 9.4.3:
	validHoleFits no evdest
  [G] 'Nothing ~# 'Just p0_aKD[tau:1]

Alternatively:

module M where

p :: (Int ~ Bool => r) -> r
p = undefined

q :: r
q = p _

Credits to Sjoerd Visscher for finding the issue.