Understanding Rust Error E0496: Lifetime Name Shadowing

Introduction to Rust Error E0496

Rust Error E0496 occurs when a lifetime name shadows another lifetime name that is already in scope. This means that the same name is being used for two different lifetimes within the same block or context, which results in ambiguity and causes the error.

Example of Rust Error E0496

#![allow(unused)]
fn main() {
struct Foo<'a> {
    a: &'a i32,
}

impl<'a> Foo<'a> {
    fn f<'a>(x: &'a i32) { // error: lifetime name `'a` shadows a lifetime name that is already in scope
    }
}
}

How to Resolve Rust Error E0496

To fix Rust Error E0496, you need to change the name of one of the lifetimes. This will remove the ambiguity and prevent the shadowing issue. In the code example below, the second lifetime parameter is renamed from `'a` to `'b` to resolve the error.

Corrected Example

struct Foo<'a> {
    a: &'a i32,
}

impl<'a> Foo<'a> {
    fn f<'b>(x: &'b i32) { // ok!
    }
}

fn main() {
}

Conclusion

Rust Error E0496 occurs when a lifetime name shadows another lifetime name within the same scope or context. To fix this error, change one of the lifetime names, ensuring there is no ambiguity between them. With the correct naming conventions in place, your Rust code should now compile and run without this error.