I found a paradox. If a knight is on d7 and a pawn is on d4, with nothing
preventing either from moving to c5, a paradox results. If the knight can
move to c5, then the pawn can't. If the pawn can, then the knight can't.
There is no way of detirmining who can move there in the rules, but try
these:
black gets priority
both can move
neither can move
the square and both pieces fall into a wormhole and vanish
creating this situation is an illegal move