Static rustc_lint::async_closures::CLOSURE_RETURNING_ASYNC_BLOCK

pub static CLOSURE_RETURNING_ASYNC_BLOCK: &Lint

The closure_returning_async_block lint detects cases where users write a closure that returns an async block.

Example

#![warn(closure_returning_async_block)]
let c = |x: &str| async {};

{{produces}}

Explanation

Using an async closure is preferable over a closure that returns an async block, since async closures are less restrictive in how its captures are allowed to be used.

For example, this code does not work with a closure returning an async block:

async fn callback(x: &str) {}

let captured_str = String::new();
let c = move || async {
    callback(&captured_str).await;
};

But it does work with async closures:

#![feature(async_closure)]

async fn callback(x: &str) {}

let captured_str = String::new();
let c = async move || {
    callback(&captured_str).await;
};