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The Ultimate Guide to Rust Programming

Lifetimes of References

Understand how Rust manages lifetimes of references to ensure memory safety. This lesson explains why references cannot outlive the values they refer to, explores the concept of lifetime elision, and introduces lifetime annotations to prevent common errors and dangling references.

We'll cover the following...

There’s an important restriction on references, both mutable and immutable, they cannot live longer than the values they are referencing. Let’s look at an example:

Rust 1.40.0
fn main() {
    let x: &i32 = {
        let y = 5;
        &y
    };
    println!("x == {}", x);
}

This program defines a new variable, y, inside a block. That block then returns a reference to y. This program fails to compile: ...