Awaiting a function returning a never type does not raise unreachable code after the await. Is this a rust or a tokio issue?

[ungrichtepfl]

Hi guys

I recently noticed that if you await a function returning the never type ! the compiler (I used rustc 1.80.0) does not warn about unreachable code after the await, i.e. writing

pub async fn endless() -> ! {
    loop {
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
    }
}

pub async fn does_not_warn_unreachable() {
    endless().await;
    println!("Hello, world!"); // No warning
}

compiles without a warning, but the non-async version

pub fn endless() -> ! {
    loop {
        std::thread::sleep(std::time::Duration::from_secs(1));
    }
}

pub fn warns_unreachable() {
    endless();
    println!("Hello, world!");  // warning: unreachable statement
}

warns about an unreachable statement after endless.

Is this a general rust async/.await issue with the never type or is this due to tokio?

Thanks for your help :)

[Darksonn]

Please file a bug with the Rust compiler instead.

[ungrichtepfl]

Moved to rust-lang/rust#128434