// Disambiguation if we have more then one piece with destination 'to'
// note that for pawns is not needed because starting file is explicit.
attackers = pos.attackers_to(to) & pos.pieces(pt, pos.side_to_move());
// Disambiguation if we have more then one piece with destination 'to'
// note that for pawns is not needed because starting file is explicit.
attackers = pos.attackers_to(to) & pos.pieces(pt, pos.side_to_move());