fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) {
        let iterator = iter.into_iter();
        let (lower, _) = iterator.size_hint();

        self.reserve(lower);

        iterator.for_each(move |elem| self.push(elem));
    }
Returns the remaining items of this iterator as a mutable slice.

# Examples

```
let vec = vec!['a', 'b', 'c'];
let mut into_iter = vec.into_iter();
assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
into_iter.as_mut_slice()[2] = 'z';
asse
benchmarks/haystacks/code/rust-library.rs