fn dupa(buf: &[u8]) {
    println!("{:?}", buf);
}

struct Message {
    body: Vec<u8>,
}

impl Into<[u8]> for Message {
    fn into(self) -> &[u8] {
        return self.body.as_slice();
    }
}

fn main() {
    let m = Message{ body: vec![1,2,3]};
    dupa(&m.into());
}