E0521 - Error codes index
Description: Book listing all Rust error codes

# Error code E0521

Borrowed data escapes outside of closure.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    let mut list: Vec<&str> = Vec::new();

    let _add = |el: &str| {
        list.push(el); // error: `el` escapes the closure body here
    };
    }

A type annotation of a closure parameter implies a new lifetime declaration. Consider to drop it, the compiler is reliably able to infer them.

    #![allow(unused)]
    fn main() {
    let mut list: Vec<&str> = Vec::new();

    let _add = |el| {
        list.push(el);
    };
    }

See the Closure type inference and annotation and Lifetime elision sections of the Book for more details.