unused_async triggers on stubs with todo!()

[trevoranderson]

Summary

Example code that triggers it

async fn unimplemented_task() -> Result<(), String> {
    todo!("Implement task");
}
warning: unused `async` for function with no await statements
    = help: consider removing the `async` from this function
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unused_async
    = note: `-W clippy::unused-async` implied by `-W clippy::pedantic`
    = help: to override `-W clippy::pedantic` add `#[allow(clippy::unused_async)]`

I expected that todo!() or unimplemented!() would silence the lint. The fix isn't helpful since the stubbed code will eventually be async, is awaited by other partially implemented code, and has the defacto type of never.

Lint Name

No response

Reproducer

I tried this code:

<code>

I saw this happen:

<output>

I expected to see this happen:

Version

Additional Labels

No response

[profetia]

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