error.txt

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter in function call due to conflicting requirements
   --> src/lib.rs:459:23
    |
459 |             Some(&mut self.sv.data[1])
    |                       ^^^^^^^^^^^^^^^
    |
note: first, the lifetime cannot outlive the lifetime 'b as defined on the body at 450:52...
   --> src/lib.rs:450:53
    |
450 |       fn next<'b>(&'b mut self) -> Option<Self::Item> {
    |  _____________________________________________________^
451 | |         if self.pos == self.sv.data.len() {
452 | |             None
453 | |         } else {
...   |
460 | |         }
461 | |     }
    | |_____^
note: ...so that reference does not outlive borrowed content
   --> src/lib.rs:459:23
    |
459 |             Some(&mut self.sv.data[1])
    |                       ^^^^^^^^^^^^
note: but, the lifetime must be valid for the lifetime 'a as defined on the body at 450:52...
   --> src/lib.rs:450:53
    |
450 |       fn next<'b>(&'b mut self) -> Option<Self::Item> {
    |  _____________________________________________________^
451 | |         if self.pos == self.sv.data.len() {
452 | |             None
453 | |         } else {
...   |
460 | |         }
461 | |     }
    | |_____^
note: ...so that types are compatible (expected std::iter::Iterator, found std::iter::Iterator)
   --> src/lib.rs:450:53
    |
450 |       fn next<'b>(&'b mut self) -> Option<Self::Item> {
    |  _____________________________________________________^
451 | |         if self.pos == self.sv.data.len() {
452 | |             None
453 | |         } else {
...   |
460 | |         }
461 | |     }
    | |_____^

iter.rs

pub struct IterMut<'a, T: 'a> {
    sv: &'a mut StableVec<T>,
    pos: usize,
}

impl<'a, T> Iterator for IterMut<'a, T> {
    type Item = &'a mut T;

    fn next<'b>(&'b mut self) -> Option<Self::Item> {
        if self.pos == self.sv.data.len() {
            None
        } else {
            while self.sv.deleted[self.pos] {
                self.pos += 1;
            }
            self.pos += 1;

            Some(&mut self.sv.data[1])  // <-- `self.sv.data` is a `Vec<T>`
        }
    }
}