use std::pin::Pin;

struct A {
    a: i32,
    b: i32,
}

impl A {
    // fn t(&mut self) {  只要self不是Pin就不会出错
    fn t(mut self: Pin<&mut Self>) {
        let b_a = &mut self.a;
        Pin::new(&mut self.b);
        *b_a = 10;
    }
}

fn main() {}