struct Container {
    elems: Vec<u8>,
}

impl Container {
    // Since we're just indexing, it would be nice to re-use CIter here
    fn iter_mut<'a>(&'a mut self) -> CIter<'a> {
        CIter {
            reference: self,
            position: 0,
        }
    }
}

struct CIter<'a> {
    reference: &'a mut Container,
    position: usize,
}

/*impl<'a> Iterator for CIter<'a> {
    type Item = &'a mut u8;

    fn next(&'a mut self) -> Option<&'a mut u8> {
        let item = self.reference.elems.get_mut(self.position);
        self.position += 1;
        item
    }
}*/

impl<'a> CIter<'a> {
    fn next(&'a mut self) -> Option<&'a mut u8> {
        let item = self.reference.elems.get_mut(self.position);
        self.position += 1;
        item
    }
}

fn main() {
    for elem in (Container { elems: vec![0, 1, 2, 3, 4, 5] }).iter_mut().next() {
        println!("{}", elem);
    }
}