Lifetime (Programming Language)

Rust has generic lifetime annotations.

Validating References with Lifetimes - The Rust Programming Language

fn main() {
    let r;                // ---------+-- 'a
                          //          |
    {                     //          |
        let x = 5;        // -+-- 'b  |
        r = &x;           //  |       |
    }                     // -+       |
                          //          |
    println!("r: {}", r); //          |
}                         // ---------+

…this returns a compiler error, because variable x does not live long enough, even though r is a valid value.