clippy::partialeq_ne_impl: re-implementing `PartialEq::ne` is unnecessary

What you see

warning: re-implementing `PartialEq::ne` is unnecessary
 --> main.rs:7:5
  |
7 |     fn ne(&self, other: &Foo) -> bool { !(self == other) }
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#partialeq_ne_impl
  = note: `#[warn(clippy::partialeq_ne_impl)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

PartialEq::ne is required to always return the negated result of PartialEq::eq, which is exactly what the default implementation does. Therefore, there should never be any need to re-implement it.

Code that does something simple in a complicated way. Warns by default.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

struct Foo;

impl PartialEq for Foo {
    fn eq(&self, other: &Foo) -> bool { true }
    fn ne(&self, other: &Foo) -> bool { !(self == other) }
}

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::partialeq_ne_impl)]
fn my_function() { /* ... */ }

[lints.clippy]
partialeq_ne_impl = "allow"

cargo clippy -- -A clippy::partialeq-ne-impl

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.