unnecessary_safety_comment false positive in _ = unsafe { foo_unsafe() } expression, conflicts with undocumented_unsafe_blocks correct analysis

[sandersaares]

Summary

The unnecessary_safety_comment lint considers a safety comment as being unnecessary if the code is of the shape:

_ = unsafe { foo_unsafe() }

The following alternative shape is correctly identified as requiring a safety comment:

let _ = unsafe { foo_unsafe() }

The undocumented_unsafe_blocks lint expects a safety comment in both cases, so the first case cannot pass Clippy check if both lints are enabled.

Lint Name

unnecessary_safety_comment

Reproducer

unsafe fn foo() -> usize {
    1234
}

#[deny(clippy::unnecessary_safety_comment)]
#[deny(clippy::undocumented_unsafe_blocks)] // For comparison
fn main() {
    // SAFETY: unnecessary_safety_comment incorrectly triggers here
    _ = unsafe { foo() };
}

Version

rustc 1.79.0 (c6bcfe6a60 2024-06-18) (1.79.0-ms-20240619.1+c6bcfe6a60)
binary: rustc
commit-hash: c6bcfe6a6082b23fa084d9690fee241c23ee9d29
commit-date: 2024-06-18
host: x86_64-pc-windows-msvc
release: 1.79.0
LLVM version: 18.1.7

Additional Labels

No response