Removing en passant doesn't work

[analog-hors]

Removing en passant moves doesn't work:

fn main() {
    let board = "8/8/5k2/8/3Pp3/8/2K5/8 b - d3 0 1".parse().unwrap();
    let mut moves = chess::MoveGen::new_legal(&board);
    let en_passant = "e4d3".parse().unwrap();
    moves.remove_move(en_passant);
    assert!(moves.find(|&mv| mv == en_passant).is_none()); //Assertion fails
}

The reason is because the code for removal makes the assumption that each SquareAndBitBoard has a unique source square, as it masks out the move and then returns:

chess/src/movegen/movegen.rs

Lines 140 to 148 in ad13857

 pub fn remove_move(&mut self, chess_move: ChessMove) -> bool { 
     for x in 0..self.moves.len() { 
         if self.moves[x].square == chess_move.get_source() { 
             self.moves[x].bitboard &= !BitBoard::from_square(chess_move.get_dest()); 
             return true; 
         } 
     } 
     false 
 } 

However, this assumption fails to hold when en passant is involved, as new SquareAndBitBoards are created for every en passant move.

chess/src/movegen/piece_type.rs

Lines 150 to 194 in ad13857

 for src in pieces & !pinned { 
     let moves = Self::pseudo_legals(src, color, *combined, mask) & check_mask; 
     if moves != EMPTY { 
         unsafe { 
             movelist.push_unchecked(SquareAndBitBoard::new( 
                 src, 
                 moves, 
                 src.get_rank() == color.to_seventh_rank(), 
             )); 
         } 
     } 
 } 
  
 if !T::IN_CHECK { 
     for src in pieces & pinned { 
         let moves = Self::pseudo_legals(src, color, *combined, mask) & line(ksq, src); 
         if moves != EMPTY { 
             unsafe { 
                 movelist.push_unchecked(SquareAndBitBoard::new( 
                     src, 
                     moves, 
                     src.get_rank() == color.to_seventh_rank(), 
                 )); 
             } 
         } 
     } 
 } 
  
 if board.en_passant().is_some() { 
     let ep_sq = board.en_passant().unwrap(); 
     let rank = get_rank(ep_sq.get_rank()); 
     let files = get_adjacent_files(ep_sq.get_file()); 
     for src in rank & files & pieces { 
         let dest = ep_sq.uforward(color); 
         if PawnType::legal_ep_move(board, src, dest) { 
             unsafe { 
                 movelist.push_unchecked(SquareAndBitBoard::new( 
                     src, 
                     BitBoard::from_square(dest), 
                     false, 
                 )); 
             } 
         } 
     } 
 } 

This leads to remove_move returning early and never actually removing the move.