`undocumented_unsafe_blocks` false positive despite `accept-comment-above-attributes = true`

Summary

undocumented_unsafe_blocks fires when attribute follows safety comment even though accept-comment-above-attributes = true is set in clippy.toml.

See https://github.com/google/zerocopy/pull/2753 for full context and another example of the failure.

Lint Name

undocumented_unsafe_blocks

Reproducer

I tried this code:

        // We use `transmute` instead of an `as` cast since Miri (with strict
        // provenance enabled) notices and complains that an `as` cast creates a
        // pointer with no provenance. Miri isn't smart enough to realize that
        // we're only executing this branch when we're constructing a zero-sized
        // `Box`, which doesn't require provenance.
        //
        // SAFETY: any initialized bit sequence is a bit-valid `*mut u8`. All
        // bits of a `usize` are initialized.
        #[allow(unknown_lints)] // For `integer_to_ptr_transmutes`
        #[allow(clippy::useless_transmute, integer_to_ptr_transmutes)]
        let dangling = unsafe { mem::transmute::<usize, *mut u8>(align) };

I saw this happen:

error: unsafe block missing a safety comment
   --> src/util/mod.rs:375:24
    |
375 |         let dangling = unsafe { mem::transmute::<usize, *mut u8>(align) };
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider adding a safety comment on the preceding line
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#undocumented_unsafe_blocks
note: the lint level is defined here
   --> src/lib.rs:272:5
    |
272 |     clippy::undocumented_unsafe_blocks,
    |    

I expected to see this happen:

No lint triggered

Version

rustc 1.93.0-nightly (20383c9f1 2025-11-03)
binary: rustc
commit-hash: 20383c9f1d84eb9b9c6668a1668ef68a81eae274
commit-date: 2025-11-03
host: x86_64-unknown-linux-gnu
release: 1.93.0-nightly
LLVM version: 21.1.3

Here's the toolchain version we're running on main, where this failure is not showing up. Presumably this is a regression introduced between these two toolchain versions.

rustc 1.92.0-nightly (53a741fc4 2025-10-16)
binary: rustc
commit-hash: 53a741fc4b8cf2d8e7b1b2336ed8edf889db84f4
commit-date: 2025-10-16
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.3

Additional Labels

No response

Start by reproducing the undocumented_unsafe_blocks diagnostic with the supplied code and accept-comment-above-attributes = true, comparing the Rust 1.92 and 1.93 nightly toolchains. Trace the lint's handling of safety comments above attributes and add a regression test; done means the reproducer emits no lint with that configuration.