- // Test discovered check and normal check according to piece type
- case KNIGHT:
- return (dcCandidates && bit_is_set(dcCandidates, from))
- || bit_is_set(piece_attacks<KNIGHT>(ksq), to);
-
- case BISHOP:
- return (dcCandidates && bit_is_set(dcCandidates, from))
- || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to));
-
- case ROOK:
- return (dcCandidates && bit_is_set(dcCandidates, from))
- || (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to));
-
- case QUEEN:
- // Discovered checks are impossible!
- assert(!bit_is_set(dcCandidates, from));
- return ( (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to))
- || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to)));
-
- case KING:
- // Discovered check?
- if ( bit_is_set(dcCandidates, from)
- && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
- return true;
+ // En passant capture with check? We have already handled the case
+ // of direct checks and ordinary discovered check, the only case we
+ // need to handle is the unusual case of a discovered check through the
+ // captured pawn.
+ if (move_is_ep(m))
+ {
+ Square capsq = make_square(square_file(to), square_rank(from));
+ clear_bit(&b, from);
+ clear_bit(&b, capsq);
+ set_bit(&b, to);
+ return (rook_attacks_bb(ci.ksq, b) & pieces(ROOK, QUEEN, us))
+ ||(bishop_attacks_bb(ci.ksq, b) & pieces(BISHOP, QUEEN, us));
+ }