Rust errors / Ownership and borrowing
Rust compiler error · checked with rustc 1.99.0
Rust error E0726: implicit elided lifetime not allowed here
What it meansAn argument lifetime was elided in an async function.
What rustc prints
error[E0726]: implicit elided lifetime not allowed here --> main.rs:8:26 | 8 | async fn create(content: Content) { // error: implicit elided | ^^^^^^^ expected lifetime parameter | help: indicate the anonymous lifetime | 8 | async fn create(content: Content<'_>) { // error: implicit elided | ++++
Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
The compiler team's explanation
An argument lifetime was elided in an async function.
Erroneous code example:
When a struct or a type is bound/declared with a lifetime it is important for the Rust compiler to know, on usage, the lifespan of the type. When the lifetime is not explicitly mentioned and the Rust Compiler cannot determine the lifetime of your type, the following error occurs.
use futures::executor::block_on;
struct Content<'a> {
title: &'a str,
body: &'a str,
}
async fn create(content: Content) { // error: implicit elided
// lifetime not allowed here
println!("title: {}", content.title);
println!("body: {}", content.body);
}
let content = Content { title: "Rust", body: "is great!" };
let future = create(content);
block_on(future);
Specify desired lifetime of parameter content or indicate the anonymous lifetime like content: Content<'_>. The anonymous lifetime tells the Rust compiler that content is only needed until the create function is done with its execution.
The implicit elision meaning the omission of suggested lifetime that is pub async fn create<'a>(content: Content<'a>) {} is not allowed here as lifetime of the content can differ from current context:
async fn create(content: Content<'_>) { // ok!
println!("title: {}", content.title);
println!("body: {}", content.body);
}
Know more about lifetime elision in this chapter and a chapter on lifetimes can be found here.
From rustc --explain E0726 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0382borrow of moved value
- E0499cannot borrow as mutable more than once at a time
- E0502cannot borrow as mutable because it is also borrowed as immutable
- E0106missing lifetime specifier
- E0713borrow may still be in use when destructor runs
- E0716temporary value dropped while borrowed
- E0745cannot take address of a temporary
- E0747type provided when a lifetime was expected
Up next
Often hit nextE0382: borrow of moved valueA related error from the same family.Read it next →Did this answer your question?