unfulfilled_lint_expectations in combination with proc macro [wasm_bingen]

[threema-theo]

Summary

clippy throws false positives when using a proc macro (I only tested with [wasm_bindgen].

I further observed the following:

• Removing #[wasm_bindgen] removes the false positive
• Removing #[expect(...)] correctly throws warnings
• Replacing #[expect(...)] with #[allow(...)] correctly removes the warnings.

I'm not 100% sure whether it is a problem of clippy or wasm-bindgen. Please tell me if the latter should be the case.

Lint Name

unfulfilled_lint_expectations

Reproducer

I tried this code:

#![warn(clippy::missing_panics_doc)]
#![warn(clippy::missing_errors_doc)]


use wasm_bindgen::prelude::wasm_bindgen;

#[expect(clippy::missing_panics_doc, reason = "mock example")]
#[wasm_bindgen]
pub fn panic() {
    panic!("Here we go");
}

#[expect(clippy::missing_errors_doc, reason = "mock example")]
#[wasm_bindgen]
pub fn error() -> Result<usize, usize> {
    Err(1)
}

I saw this happen:

    Checking playground v0.0.1 (/playground)
warning: this lint expectation is unfulfilled
 --> src/main.rs:7:10
  |
7 | #[expect(clippy::missing_panics_doc, reason = "mock example")]
  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: mock example
  = note: `#[warn(unfulfilled_lint_expectations)]` on by default

warning: this lint expectation is unfulfilled
  --> src/main.rs:13:10
   |
13 | #[expect(clippy::missing_errors_doc, reason = "mock example")]
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: mock example

warning: `playground` (bin "playground") generated 2 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.05s

I expected to see this happen: Clippy throws no warnings.

When I remove the expect macros, Clippy correctly throws the warnings.

Version

1.86.0-nightly
2025-01-15 419b3e2d3e350822550e

(see playground)

Additional Labels

No response

[samueltardieu]

wasm_bindgen applies identical outer attributes to the autogenerated code, which will not fullfill the expectations. I have proposed a patch to wasm_bindgen which transforms those attribute into equivalent #[allow] attributes in rustwasm/wasm-bindgen#4409.