`duplicated_attributes` lint no longer emitted for `#[cfg(test)]` when switching from 1.93 -> 1.94

[obi1kenobi]

Summary

Duplicating #[cfg(test)] between a module's declaration in lib.rs and its contents (either as a separate file or inlined) no longer raises clippy::duplicated_attributes in Rust 1.94+. This is a regression from 1.93.1 and earlier. Please see repro below.

Lint Name

duplicated_attributes

Reproducer

I tried this code:

#[cfg(test)]
#[allow(clippy::mixed_attributes_style, reason = "normally the module is a separate file; inlined here for simplicity")]
mod test_util {
    #![expect(
        clippy::duplicated_attributes,
        reason = "defensively specifying cfg(test) both inside `test_util.rs` and when the module is declared in `mod.rs`"
    )]
    #![cfg(test)]

    pub(crate) fn some_util() -> u64 {
        42
    }
}

#[cfg(test)]
#[test]
fn my_test() {
    assert_eq!(test_util::some_util(), 42);
}

I expected to see this happen: clippy::duplicated_attributes is raised, matching the behavior of clippy in Rust 1.93 and earlier.

$ cargo +1.93 clippy --all-targets -- -Dwarnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.04s

Instead, this happened: clippy::duplicated_attributes is not raised, and the lint expectation is unfulfilled.

$ cargo +stable clippy --all-targets -- -Dwarnings
    Checking example v0.1.0 (/tmp/example)
error: this lint expectation is unfulfilled
 --> src/lib.rs:5:9
  |
5 |         clippy::duplicated_attributes,
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: defensively specifying cfg(test) both inside `test_util.rs` and when the module is declared in `mod.rs`
  = note: `-D unfulfilled-lint-expectations` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(unfulfilled_lint_expectations)]`

error: could not compile `example` (lib test) due to 1 previous error

Version

rustc 1.94.0 (4a4ef493e 2026-03-02)
binary: rustc
commit-hash: 4a4ef493e3a1488c6e321570238084b38948f6db
commit-date: 2026-03-02
host: x86_64-unknown-linux-gnu
release: 1.94.0
LLVM version: 21.1.8

$ cargo +stable clippy --version
clippy 0.1.94 (4a4ef493e3 2026-03-02)

[obi1kenobi]

While poking around for what changed in 1.94, I noticed this PR which seems to likely be relevant here: rust-lang/rust#150310

cc @jdonszelmann @JonathanBrouwer for visibility

[JonathanBrouwer]

This is because trace attributes are now a little special in the AST, for performance reasons they are stored in a parsed form, so this check returns None: https://github.com/rust-lang/rust/blob/d9385437c20f4f7fb60fced9dd2d2d37a004dcf4/src/tools/clippy/clippy_lints/src/attrs/duplicated_attributes.rs#L86

When I have a little more time and energy I'll think about what a nice solution for this is, because I'd love if we wouldn't have to special-case trace attributes. I'll claim this issue to keep it on my backlog, but might take a while for me to get around to it, so if anyone feels like doing it feel free to steal my claim
@rustbot claim