I tried this code:

use std::process::ExitCode;

enum Never {}

fn never_returns() -> Never {
    todo!()
}

pub fn run() -> ExitCode {
    never_returns();
    ExitCode::FAILURE
}

And rustc raises an "unreachable expression" warning. This seems reasonable. So I remove that line:

use std::process::ExitCode;

enum Never {}

fn never_returns() -> Never {
    todo!()
}

pub fn run() -> ExitCode {
    never_returns();
}

I expected to see this happen:

• either rustc can tell that that path is unreachable, and it should not have type errors,
• or rustc can't tell it's unreachable, and the "unreachable expression" warning should not appear.

Instead, this happened: rustc seems to simultaneously indicate that path is unreachable, AND some expression is needed there to satisfy the type-checker.

Is there really no way to write the run function without invoking #[allow(unreachable_code)]? That seems odd. (Sorry, I shouldn't have asked. Didn't mean to nerd-snipe.)

Meta

rustc --version --verbose:

rustc 1.93.1 (01f6ddf75 2026-02-11)
binary: rustc
commit-hash: 01f6ddf7588f42ae2d7eb0a2f21d44e8e96674cf
commit-date: 2026-02-11
host: x86_64-unknown-linux-gnu
release: 1.93.1
LLVM version: 21.1.8

(Happens on any stable version >= 1.92.0; and also on nightly 2026-02-11)