clippy::non_canonical_partial_ord_impl warns for canonical forwarding implementation

[hrxi]

Lint Name

clippy::non_canonical_partial_ord_impl

Reproducer

use std::cmp::Ordering;

struct A {
    inner: i32,
    cache: i32,
}

impl PartialEq for A {
    fn eq(&self, other: &A) -> bool {
        self.inner == other.inner
    }
}

impl Eq for A {}

impl PartialOrd for A {
    fn partial_cmp(&self, other: &A) -> Option<Ordering> {
        self.inner.partial_cmp(&other.inner)
    }
}

impl Ord for A {
    fn cmp(&self, other: &A) -> Ordering {
        self.inner.cmp(&other.inner)
    }
}

Results in this warning:

warning: non-canonical implementation of `partial_cmp` on an `Ord` type
  --> 16:1
   |
16 | /  impl PartialOrd for A {
17 | |      fn partial_cmp(&self, other: &A) -> Option<Ordering> {
   | | __________________________________________________________-
18 | ||         self.inner.partial_cmp(&other.inner)
19 | ||     }
   | ||_____- help: change this to: `{ Some(self.cmp(other)) }`
20 | |  }
   | |__^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#non_canonical_partial_ord_impl
   = note: `#[warn(clippy::non_canonical_partial_ord_impl)]` on by default

But I expected no warning for this rather canonical forwarding of traits to one particular member.

Version

rustc 1.84.0 (9fc6b4312 2025-01-07)
binary: rustc
commit-hash: 9fc6b43126469e3858e2fe86cafb4f0fd5068869
commit-date: 2025-01-07
host: x86_64-unknown-linux-gnu
release: 1.84.0
LLVM version: 19.1.5