False positive for `infinite_loop` inside `async` block in function

[jwodder]

Summary

The infinite_loop lint triggers on infinite loops inside async blocks inside functions that don't return !, even if the functions don't await those blocks.

Lint Name

infinite_loop

Reproducer

I tried this code:

pub fn install_ticker() {
    let mut schedule = tokio::time::interval(std::time::Duration::from_secs(5));
    tokio::spawn({
        async move {
            loop {
                schedule.tick().await;
                println!("Tick");
            }
        }
    });
}

with this Cargo.toml:

[package]
name = "loop-bug"
version = "0.1.0"
edition = "2021"

[dependencies]
tokio = { version = "1.43.0", features = ["rt", "time"] }

[lints.clippy]
infinite_loop = "deny"

When I ran cargo clippy, I saw this happen:

    Checking loop-bug v0.1.0 (/Users/jwodder/work/dev/tmp/loop-bug)
error: infinite loop detected
 --> src/lib.rs:5:13
  |
5 | /             loop {
6 | |                 schedule.tick().await;
7 | |                 println!("Tick");
8 | |             }
  | |_____________^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#infinite_loop
  = note: requested on the command line with `-D clippy::infinite-loop`
help: if this is intentional, consider specifying `!` as function return
  |
1 | pub fn install_ticker() -> ! {
  |                         ++++

error: could not compile `loop-bug` (lib) due to 1 previous error

I expected to see this happen: no errors

Version

rustc 1.84.0 (9fc6b4312 2025-01-07)
binary: rustc
commit-hash: 9fc6b43126469e3858e2fe86cafb4f0fd5068869
commit-date: 2025-01-07
host: x86_64-apple-darwin
release: 1.84.0
LLVM version: 19.1.5

Additional Labels

No response

[blyxyas]

As a tip for solvers: You can get the type of an expression with cx.tcx.expr_ty(<expr>), go the the lint's check function and start from there

[odysa]

@rustbot claim