streamer_2.rs

trait Streamer<'a> {
    type Item;
    fn next(&'a mut self) -> Option<Self::Item>;
}

struct SelfStreaming;

impl<'a> Streamer<'a> for SelfStreaming {
    type Item = &'a mut Self;
    fn next(&'a mut self) -> Option<&'a mut Self> {
        Some(self)
    }
}

fn main() {
    let mut foo = SelfStreaming;
    let a = foo.next();
    foo.next();
}