unit_cmp: don't lint on explicitly written units #15559
Description
Summary
Sometimes it's useful to be able to explicitly compare against () in test assertions (e.g. generated code). IMO clippy's unit_cmp should not lint on explicitly written () within assertions, as e.g.
assert_eq!(field, ());is more obvious intention-wise than
let () = field;Lint Name
unit_cmp
Reproducer
I tried this code:
fn main() {
struct Generated { field: () }
assert_eq!(Generated { field: () }.field, ());
}I saw this happen:
error: `assert_eq` of unit values detected. This will always succeed
--> src/main.rs:3:5
|
3 | assert_eq!(Generated { field: () }.field, ());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unit_cmp
= note: `#[deny(clippy::unit_cmp)]` on by default
I expected to see this happen:
- No errors because RHS
()is explicitly spelled out, and user intention is clear.
Version
rustc 1.89.0 (29483883e 2025-08-04)
binary: rustc
commit-hash: 29483883eed69d5fb4db01964cdf2af4d86e9cb2
commit-date: 2025-08-04
host: aarch64-apple-darwin
release: 1.89.0
LLVM version: 20.1.7
Additional Labels
No response