The Issue

I’m trying to implement an iterator that yields windows (i.e. slices) into a buffer owned by the iterator itself – for example, if the buffer contains [0, 1, 2, 3, 4, 5], the iterator might yield [0, 1, 2, 3], [2, 3], or [3, 4, 5]. Here’s a minimal example (Playground):

struct Slicer<'a> {
    full: Vec<u32>,
    cur_slice: &'a mut [u32]
}

impl<'a> Slicer<'a> {
    fn new() -> Slicer<'a> {
        let mut full = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
        Slicer {
            full: full, // Is there a way to transfer ownership of `full` here?
            cur_slice: full.as_mut_slice()
        }
    }
}

impl<'a> Iterator for Slicer<'a>
{
    type Item = &'a [u32];

    fn next(&mut self) -> Option<&'a [u32]> {
        if self.cur_slice.len() != 0 {
            // In the actual program, this is streaming new data into the
            // buffer. This is just an example of modifying the slice.
            let len = self.cur_slice.len();
            self.cur_slice = self.cur_slice[..len - 1].as_mut();
            Some(self.cur_slice) // Getting a lifetime error here…
        } else {
            None
        }
    }
}

fn main() {
    let mut slicer = Slicer::new();
    while let Some(x) = slicer.next() {
        println!("{x:?}");
    }
}

This results in two separate errors: error[E0515]: cannot return value referencing local variable `full` and error: lifetime may not live long enough. Full errors:

error[E0515]: cannot return value referencing local variable `full`
  --> srcmain.rs:11:9
   |
11 | /         Slicer {
12 | |             full: full,
13 | |             cur_slice: full.as_mut_slice()
   | |                        ---- `full` is borrowed here
14 | |         }
   | |_________^ returns a value referencing data owned by the current function

error: lifetime may not live long enough
  --> srcmain.rs:26:13
   |
16 | impl<'a> Iterator for Slicer<'a>
   |      -- lifetime `'a` defined here
...
20 |     fn next(&mut self) -> Option<&'a [u32]> {
   |             - let's call the lifetime of this reference `'1`
...
26 |             Some(self.cur_slice) // Getting a lifetime error here…
   |             ^^^^^^^^^^^^^^^^^^^^ method was supposed to return data with lifetime `'a` but it is returning data with lifetime `'1`

Now, from what I understand, this counts as an iterator that refers to itself – which an Iterator is unable to do (because the signature of next doesn’t include an explicit lifetime for &mut self – with fairly good reason, from what I understand). This appears to be a perfect use case for lending iterators (as mentioned in this previous StackOverflow answer, and in fact, a window iterator is the primary example in the docs), but I attempted an implementation using a lending iterator, and was presented with exactly the same errors.

The Question

How does one fix this? Is there a way to make the lending iterator approach work? Is there a different composition that achieves the same effect?

(Note that I can’t copy the data, as that would defeat the purpose of the iterator, which is meant to be a more ergonomic interface into parsing a particular file format with a lot of data.)