file.rs

for x in 0..map.width {
    let entity = match map.tiles.get(&(x, y)) {
        Some(entity) => *entity,
        None => {
            let entity = entities.create();
            map.tiles.insert((x, y), entity);

            entity
        }
    };

    kinds.insert(entity, EntityKind::Empty).unwrap();
    positions.insert(entity, Position::new(x, y)).unwrap();

    map.tiles.insert((x, y), entity);
}

match-destruction

error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
   --> src/systems.rs:212:34
    |
212 |                       let entity = match map.tiles.get(&(x, y)) {
    |  __________________________________^
213 | |                         Some(entity) => *entity,
214 | |                         None => {
215 | |                             let entity = entities.create();
...   |
219 | |                         }
220 | |                     };
    | |_____________________^