Rust code shared from the playground

playground.rs

use std::cell::RefCell;

struct Foo<'a> {
    items: Vec<u8>,
    cur_item: RefCell<Option<&'a u8>>
}

impl<'a> Foo<'a> {
    fn mutate(&mut self) {}
}

fn main() {
    let mut foo = Foo {
        items: vec![0],
        cur_item: RefCell::new(None),
    };
    
    *foo.cur_item.borrow_mut() = Some(&foo.items[0]);
    
    foo.mutate();
}