clippy::redundant_async_block: this async expression only awaits a single future

What you see

warning: this async expression only awaits a single future
 --> main.rs:6:11
  |
6 |   let fut = async {
  |  ___________^
7 | |     f.await
8 | | };
  | |_^ help: you can reduce it to: `f`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#redundant_async_block
  = note: `#[warn(clippy::redundant_async_block)]` 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?

It is simpler and more efficient to use the future directly.

Code that does something simple in a complicated way. Warns by default.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

let f = async {
    1 + 2
};
let fut = async {
    f.await
};

Write this instead

let f = async {
    1 + 2
};
let fut = f;

Turn it off, or on

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

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

[lints.clippy]
redundant_async_block = "allow"

cargo clippy -- -A clippy::redundant-async-block

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.