struct Coord {
    x: i8,
    y: i8,
}

struct GameBoard {
    board: [[char; 3]; 3],
    mine: Coord,
}

impl GameBoard {
    fn new() -> GameBoard {
        // Generate the mine position
        let x = rand::thread_rng().gen_range(0, 2);
        let y = rand::thread_rng().gen_range(0, 2);

        GameBoard {
            board: [
                [O, O, O],
                [O, O, O],
                [O, O, O]
            ],
            mine: Coord {x: x, y: y},
        }
    }
}

fn update_board(game_board: &mut GameBoard, coord: &Coord) {
    if game_board.mine.x == coord.x && game_board.mine.y == coord.y {
        // error: the trait `core::ops::Index<i8>` is not implemented for the type `[[char; 3]]` [E0277]
        game_board.board[coord.x][coord.y] = BOMB;
    }
}