use futures::FutureExt;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

enum State {
    A(i32),
}

struct MyFuture {
    rx: Pin<Box<dyn Future<Output = i32> + Send>>,
    state: State,
}
/*
impl Future for MyFuture {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        loop {
            match &mut self.state {
                State::A(n) => {
                    match self.rx.poll_unpin(cx) {
                        Poll::Ready(_) => {
                        }
                        _ => unimplemented!(),
                    }
                    *n = 10; // 只要有这句就报错
                },
            }
        }
    }
}*/

fn main() {
    struct A {
        a: i32,
        b: i32,
    }

    let mut a = A { a: 10, b: 10 };
    let b_a = &mut a.a;
    let b_b = &mut a.b;
    *b_b = 30;
    *b_a = 20;
}