enum Piece{}
type Tile = Option<Piece>;

struct Game {
    board: [Tile; 64],
}

impl Game {
    fn tiles(&self) -> impl Iterator< Item = ((usize, usize), &Tile) > {
        self.board
            .chunks(8)
            .enumerate()
            .flat_map(|(y, row)| row.iter().enumerate().map(move |(x, tile)| ((x, y), tile)))
    }
}