`unnecessary_safety_comment` and `undocumented_unsafe_blocks` visit the same comment twice

[teofr]

Summary

When having a SAFETY comment on top of a statement that has an unsafe block, the statement is needed for the block, but is also linted for the (safe) statement.

I'm not entirely sure the best way to fix it easily, but I think a bigger refactor around these lints are needed, where:

• first SAFETY comments are gathered,
• then each unsafe block is linked to a given SAFETY comment,
• and finally lints are emitted accordingly

Reproducer

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=07e7366f10d4bd79f6257b50dce7f9a5

I tried this code:

#![warn(clippy::undocumented_unsafe_blocks, clippy::unnecessary_safety_comment)]
#![no_main]

use std::num::NonZeroI32;

struct Date {
    value: NonZeroI32,
}

impl Date {
    const unsafe fn __from_ordinal_date_unchecked(year: i32, ordinal: u16) -> Self {
        Self {
            // Safety: The caller must guarantee that `ordinal` is not zero.
            value: unsafe { NonZeroI32::new_unchecked((year << 9) | ordinal as i32) },
        }
    }

    const fn into_julian_day_just_make_this_line_longer(self) -> i32 {
        42
    }
}

unsafe fn foo() {
    /// The Julian day of the Unix epoch.
    // SAFETY: fail ONLY if `accept-comment-above-attribute = false`
    const UNIX_EPOCH_JULIAN_DAY: i32 = unsafe { Date::__from_ordinal_date_unchecked(1970, 1) }
        .into_julian_day_just_make_this_line_longer();

    /// The Julian day of the Unix epoch.
    const UNIX_EPOCH_JULIAN_DAY_2: i32 = unsafe { Date::__from_ordinal_date_unchecked(1970, 1) }
        .into_julian_day_just_make_this_line_longer();

}

I expected to see this happen:

No lints around UNIX_EPOCH_JULIAN_DAY

Instead, this happened:

warning: constant has unnecessary safety comment
  --> src/lib.rs:26:5
   |
26 |     const UNIX_EPOCH_JULIAN_DAY: i32 = unsafe { Date::__from_ordinal_date_unchecked(1970, 1) }
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: consider removing the safety comment

Version

rustc 1.92.0-nightly (4645a7988 2025-09-17)
binary: rustc
commit-hash: 4645a7988177c286f61609cc667ecae4c571a2e8
commit-date: 2025-09-17
host: aarch64-apple-darwin
release: 1.92.0-nightly
LLVM version: 21.1.1

Additional Labels

@rustbot label +I-false-positive

[zihan0822]

Current impl does not consider UNIX_EPOCH_JULIAN_DAY as unsafe because there is a method call outside the unsafe block. It won't lint if you put the safety comment above the unsafe block or move the method call inside the unsafe block.

Check this:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=44a514d26892ede289f1bf9cc38757a8