struct A {
    b: B,
    c: C,
}

#[derive(Clone)]
struct B {}

struct C {}

impl A {
    fn some_action(&mut self) -> B {
        //some actions with self.b
        // return self.b
        return self.b.clone();
    }
}

fn main() {
    let mut a = A { b: B {}, c: C {} };
    let b = a.some_action();
}