streamer_1.rs

trait ApplyLTable<'to> {
    type Applied;
}

impl<'from, 'to, T: 'from+'to> ApplyLTable<'to> for &'from T {
    type Applied = &'to T;
}

impl<'from, 'to, T: 'from+'to> ApplyLTable<'to> for &'from mut T {
    type Applied = &'to mut T;
}

type ApplyLT<'lt, T> = <T as ApplyLTable<'lt>>::Applied;

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

struct SelfStreaming;

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

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