Lifetimes

https://corrode.dev/blog/lifetimes/

Play

fn example_1() {
    let r;

    {
        let x = 42;
        r = &x;
    }

    println!("{}", *r);
}

fn example_2() {
    let foo = 69;
    let mut r;

    {
        let x = 42;
        r = &x;

        println!("{}", *r)
    }

    r = &foo;

    println!("{}", *r);
}