wrong_self_convention false positive?

[leonardo-m]

trait Foo {
    fn from_usize(x: usize) -> Self;
}
impl Foo for usize {
    fn from_usize(x: usize) -> Self { x }
}
fn main() {}

Gives:

warning: methods called `from_*` usually take no `self`
 --> src/main.rs:5:19
  |
5 |     fn from_usize(x: usize) -> Self { x }
  |                   ^
  |
  = note: `#[warn(clippy::wrong_self_convention)]` on by default
  = help: consider choosing a less ambiguous name
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#wrong_self_convention

But this from_usize isn't taking self.