In Rust, there's a `#[must_use]` attribute that can be applied to types, such as Result, and on functions. This triggers if the return value is not used. It's only a warning though, but you could imagine a hypothetical imperative language making this a hard error

#![deny(must_use)] on the root of your crate makes it a hard error for your whole crate.

Typically what happens is that having this set on is very annoying while developing code, because we often want to test incomplete code without proper error handling before we finish it. So sometimes people will block on this kind of issue in CI, but not error out during development (a warning is more than enough)