How to box a dyn trait with interface function consume itself?

Question

From https://doc.rust-lang.org/rust-by-example/trait/dyn.html , as known, the dyn trait's size is not known when compiling, so we can not use it as a return value. But when can create a reference and put it in box, the box has fixed size.

But I met a problem, how can I box a tait which has an interface to consume it.

#[tokio::test]
async fn test_dyn_trait() {
    trait Consume {
        fn usage(self) -> String;
    }
    trait Refer {
        fn usage(&self) -> String;
    }

    struct Man {
        name: String,
    }
    impl Consume for Man {
        fn usage(self) -> String {
            let Man { name } = self;
            return name;
        }
    }
    impl Refer for Man {
        fn usage(&self) -> String {
            return self.name.clone();
        }
    }

    let a: Box<dyn Consume> = Box::new(Man {
        name: "aaron".to_string(),
    });
    let b: Box<dyn Refer> = Box::new(Man {
        name: "aaron".to_string(),
    });
    println!("a: {}", a.usage()); // cannot move a value of type dyn Consume: the size of dyn Consume cannot be statically determined
    println!("b: {}", b.usage()); // it is ok
}

Answer 1

This is impossible. Rust has something called object safety , which prevent creating trait objects of traits that have a method that either takes or returns Self (and couple other things).