#[derive(Debug, Clone)]
struct Stu {
    name: String,
    age: u32,
}

impl Drop for Stu {
    fn drop(&mut self) {
        println!("Dropping CustomSmartPointer with data `{:?}`!", self);
    }
}
fn main() {
    let mut s = Stu {
        age: 11,
        name: String::from("ace"),
    };

    println!("{:?}", s);
    s.age = 22;
    s.name = String::from("root");
    println!("{:?}", s);

    let s2 = &s;
    println!("{:?} {:?}", s2, s);

    // 报错, 借用没被回收时, 不能改
    // s.age = 33;
    // println!("{:?} {:?}", s2, s);

    let s3 = s.clone();
    s.age = 33;
    println!("{:?} {:?}", s3, s);
}