case DELTA_SE:
// Capture. The destination square must be occupied by an enemy
// piece (en passant captures was handled earlier).
- if (color_of_piece_on(to) != them)
- return false;
- break;
+ if (color_of_piece_on(to) != them)
+ return false;
+
+ // From and to files must be one file apart, avoids a7h5
+ if (abs(square_file(from) - square_file(to)) != 1)
+ return false;
+ break;
case DELTA_N:
case DELTA_S:
// Pawn push. The destination square must be empty.
- if (!square_is_empty(to))
- return false;
- break;
+ if (!square_is_empty(to))
+ return false;
+ break;
case DELTA_NN:
// Double white pawn push. The destination square must be on the fourth
|| !square_is_empty(to)
|| !square_is_empty(from + DELTA_N))
return false;
- break;
+ break;
case DELTA_SS:
// Double black pawn push. The destination square must be on the fifth
// rank, and both the destination square and the square between the
// source and destination squares must be empty.
- if ( square_rank(to) != RANK_5
- || !square_is_empty(to)
- || !square_is_empty(from + DELTA_S))
- return false;
- break;
+ if ( square_rank(to) != RANK_5
+ || !square_is_empty(to)
+ || !square_is_empty(from + DELTA_S))
+ return false;
+ break;
default:
return false;