struct TestObject {
    v: i32
}
trait DropSelf {
    fn drop_self(&mut self) {
        println!("---- drop_self call");
    }
}
impl TestObject {
    fn show(v: &mut i32) {
        println!("show called {}",v);
    }
    fn test_mut(&mut self) {
        //self.v += 1;
        println!("self.v = {}", self.v);
    }
}

impl Drop for TestObject {
    //我这里的函数签名是&mut self,但我传一个引用，也可以i编译过
    fn drop(&mut self) {
        self.drop_self();
        println!("drop called");
    }


}

impl DropSelf for TestObject {}

fn main() {
    let m = TestObject {v:1};
    let mut data = 2;
    TestObject::show(&mut data); //这样就无法编译
    //drop(m);
    //m.test_mut();
    m.drop_self();
}