Shared via Rust Playground

playground.rs

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

struct Buffer<T> {
    data: Vec<T>,
    pos: usize
}

impl<'a, T: 'a> StreamingIterator<'a> for Buffer<T> {
    type Item = &'a T;
    fn next(&'a mut self) -> Option<&'a T> {
        let x = self.data.get(self.pos);
        self.pos += 1;
        x
    }
}

impl<'a, I: Iterator> StreamingIterator<'a> for I {
    type Item = I::Item;
    fn next(&mut self) -> Option<I::Item> {
        Iterator::next(self)
    }
}

fn cloned_collect<T, I>(mut iter: I) -> Vec<T>
    where I: for<'a> StreamingIterator<'a, Item=&'a T>,
          T: Clone
{
    let mut v = vec![];
    while let Some(x) = iter.next() {
        v.push(x.clone());
    }
    v
}

fn old_collect<T, I>(mut iter: I) -> Vec<T>
    where I: for<'a> StreamingIterator<'a, Item=T>
{
    let mut v = vec![];
    while let Some(x) = iter.next() {
        v.push(x);
    }
    v
}


fn main() {
    println!("{:?}", old_collect(
        cloned_collect(Buffer {
            data: vec![0u8, 2, 3, 5],
            pos: 1
        }).iter()
    ));
    
}