derive-combine

```rust use derive_combine::Combine;

[derive(Combine, Eq, PartialEq, Debug)]

struct Abc { a: Option, b: Vec, d: u16, }

[test]

fn test_combine() { let mut abc = Abc { a: Some(1), b: vec![2], d: 3, };

let other = Abc {
    a: None,
    b: vec![4],
    d: 5,
};

abc.combine(other);

let expected = Abc {
    a: Some(1),
    b: vec![2, 4],
    d: 3,
};

assert_eq!(abc, expected);

} ```