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Fixing Rust Error E0726: Argument Lifetime Elision

Introduction to Rust Error E0726

Rust Error E0726 occurs when an argument lifetime is elided in an async function. Lifetime elision is a feature in Rust that allows the omission of explicit lifetime annotations in function signatures. However, for async functions, implicit elision of lifetimes is not allowed.

Analyzing the Erroneous Code Example

Consider the following erroneous code example, which triggers Rust Error E0726:

```rust
#![allow(unused)]
fn main() {
  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);
}
```

The error occurs because the async function 'create' takes '*Content*' as a parameter, but the lifetime of the Content struct is not specified. Implicit lifetime elision is not allowed, and the Rust compiler requires an explicit lifetime annotation in this case.

Solution: Specify the Lifetime

To fix Rust Error E0726, you need to specify the desired lifetime of the parameter content or use the anonymous lifetime '_':

```rust
async fn create(content: Content<'_>) { // ok!
    println!("title: {}", content.title);
    println!("body: {}", content.body);
}
```

The anonymous lifetime '_ tells the Rust compiler that the content is only needed until the create function is done with its execution.

For more information on lifetime elision and lifetimes in Rust, refer to the recommended articles in the Recommended Reading section.

Recommended Reading