You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: io_read.rs
    path of file: ./repos/kani/tests/slow/tokio-proofs/src/tokio
    
    the code of the file until where you have to start completion: // SPDX-License-Id
    
async fn read() {
    #[derive(Default)]
    struct Rd {
        poll_cnt: usize,
    }

    impl AsyncRead for Rd {
        fn poll_read(
            mut self: Pin<&mut Self>,
            _cx: &mut Context<'_>,
            buf: &mut ReadBuf<'_>,
        ) -> Poll<io::Result<()>> {
            assert_eq!(0, self.poll_cnt);
            self.poll_cnt += 1;

            buf.put_slice(b"hello world");
            Poll::Ready(Ok(()))
        }
    }

    let mut buf = Box::new([0; 11]);
    let mut rd = Rd::default();

    let n = assert_ok!(rd.read(&mut buf[..]).await);
    assert_eq!(n, 11);
    assert_eq!(buf[..], b"hello world"[..]);
}