pub async fn endless_async() -> ! {
 loop {
 tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
 }
}
pub async fn should_warn() {
 endless_async().await;
 println!("This code is unreachable"); // no warning about unreachable code
}
pub fn endless() -> ! {
 loop {
 std::thread::sleep(std::time::Duration::from_secs(1));
 }
}
pub fn warns() {
 endless();
 println!("This code is unreachable"); // warning: unreachable statement
}

warning: unreachable statement
 --> src/lib.rs:20:5
 |
19 | endless();
 | --------- any code following this expression is unreachable
20 | println!("This code is unreachable");
 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unreachable statement
 |
 = note: `#[warn(unreachable_code)]` on by default
 = note: this warning originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: unreachable statement
 --> src/lib.rs:9:5
 |
 8 | endless_async().await;
 | --------------------- any code following this expression is unreachable
 9 | println!("This code is unreachable");
 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unreachable statement
 |
 = note: `#[warn(unreachable_code)]` on by default
 = note: this warning originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
warning: unreachable statement
 --> src/lib.rs:20:5
 |
19 | endless();
 | --------- any code following this expression is unreachable
20 | println!("This code is unreachable");
 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unreachable statement
 |
 = note: `#[warn(unreachable_code)]` on by default
 = note: this warning originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)

rustc 1.80.0 (051478957 2024年07月21日)
binary: rustc
commit-hash: 051478957371ee0084a7c0913941d2a8c4757bb9
commit-date: 2024年07月21日
host: x86_64-unknown-linux-gnu
release: 1.80.0
LLVM version: 18.1.7

rustc 1.82.0-nightly (f8060d282 2024年07月30日)
binary: rustc
commit-hash: f8060d282d42770fadd73905e3eefb85660d3278
commit-date: 2024年07月30日
host: x86_64-unknown-linux-gnu
release: 1.82.0-nightly
LLVM version: 18.1.7