#[expect(...)] attribute not working for clippy::unsafe_derive_deserialize

[B14CK313]

Summary

The #[expect(clippy::unsafe_derive_deserialize)] attribute (enabled by the lint_reasons feature) doesn't suppress the warning about deriving serde::Deserialize on a struct with an unsafe fn.
At the same time the expect attribute gives a warning about the lint expectation being unfulfilled.

At first glance this looked like the same bug as rust#119358 but in that case the warning got suppressed, which isn't the case here.

If this issue is not caused by clippy, I am happy to copy this issue over to the rust repo.

Reproducer

I tried this code:

#![feature(lint_reasons)]
#![warn(clippy::unsafe_derive_deserialize)]

#[expect(clippy::unsafe_derive_deserialize)]
#[derive(serde::Deserialize)]
struct Foo {}

impl Foo {
    #[allow(dead_code)]
    unsafe fn unsafe_fn(&self) {
        todo!()
    }
}

Playground

I expected to see this happen:
No warning emitted.

Instead, this happened:
Two warnings get emitted:

• warning: you are deriving `serde::Deserialize` on a type that has methods using `unsafe`
• warning: this lint expectation is unfulfilled

Version

rustc: 1.80.0-nightly (2024-05-14 8387315ab3c26a57a1f5)
clippy: 0.1.80 (2024-05-14 8387315)

Additional Labels

No response