clippy::async_yields_async: an async construct yields a type which is itself awaitable

What you see

error: an async construct yields a type which is itself awaitable
 --> main.rs:7:5
  |
6 |     let x = async {
  |  _________________-
7 | |     foo()
  | |     ^^^^^
  | |     |
  | |     awaitable value not awaited
  | |     help: consider awaiting this value: `foo().await`
8 | |   };
  | |___- outer async construct
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#async_yields_async
  = note: `#[deny(clippy::async_yields_async)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

An await is likely missing.

Code that is almost certainly wrong. Denied by default: the build fails until you fix it or allow it.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

async fn foo() {}

fn bar() {
  let x = async {
    foo()
  };
}

Write this instead

async fn foo() {}

fn bar() {
  let x = async {
    foo().await
  };
}

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::async_yields_async)]
fn my_function() { /* ... */ }

[lints.clippy]
async_yields_async = "allow"

cargo clippy -- -A clippy::async-yields-async

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.