enum Load {
    Idle(i32),
    Busy(i32),
}

struct Cpu {
    ld: Load,
}

fn add(t: &mut Cpu, u: &Cpu) {
    match t.ld {
        Load::Idle(i1) => match u.ld {
            Load::Idle(i2) => t.ld = Load::Idle(i1+i2),
            _ => {},
        },
        Load::Busy(i1) => match u.ld {
            Load::Busy(i2) => t.ld = Load::Busy(i1+i2),
            _ => {},
        },
    }
}

/* * /
// Compiler error:
//28 |     match (t.ld, u.ld) {
//   |            ^ cannot move out of borrowed content
fn add2(t: &mut Cpu, u: &Cpu) {
    match (t.ld, u.ld) {
        (Load::Idle(i1), Load::Idle(i2)) => t.ld = Load::Idle(i1+i2),
        (Load::Busy(i1), Load::Busy(i2)) => t.ld = Load::Busy(i1+i2),
        _ => {},
    }
}
/ * */

fn main() {
    let mut v1 = Cpu{ld: Load::Idle(10),};
    let v2 = Cpu{ld: Load::Busy(3),};
    add(&mut v1, &v2);
    match v1.ld {
        Load::Idle(i) => println!("Idle: {} ns", i),
        Load::Busy(i) => println!("Busy: {} ns", i),
    }
}