lint unused (clippy) allow attributes

[matthiaskrgr]

fn main() {
    #[cfg_attr(feature = "cargo-clippy", allow(useless_format))]
    let _ = String::from("hello");
}

It would be nice to have a message here that allow(uselss_format) is itself not effective and can be removed.
Basically I'd like to have unused clippy warning suppression linted. :)

[EdJoPaTo]

I am used to having this on JavaScript / TypeScript with no-unused-disable

unused is probably not a well chosen name for Rust / Clippy as it already has a different meaning. Still I think it could be inspiring.

[xFrednet]

Implementing a lint for this is sadly rather difficult. RFC 2383 has proposed adding a #[expect] attribute that allows lints until they no longer are emitted. The implementation is sadly not trivial and held up on some implementation details. See rust-lang/rust#54503 and my implementation draft in rust-lang/rust#87835 if you want to know the current state of the implementation. Having a feature like this would definitely help a lot!