Unable to allow unused_self after enabling pedantic

[martinthomson]

This code:

#![deny(warnings)]
#![warn(clippy::pedantic)]

struct X {}
impl X {
    #[allow(clippy::unused_self, clippy::cast_possible_truncation)]
    fn test(&self, a: u32) {
        println!("testing {}", a as u16);
    }
}
pub fn main() {
    let x = X {};
    x.test(1);
}

This correctly suppresses the clippy::cast_possible_truncation warning, but fails to suppress the clippy::unused_self.

The rust playground is currently at 0.0.212 (2019-12-29 c807fbc).
The same error is produced by clippy 0.0.212 (c8e3cfb 2019-10-28).
Older versions I have access to, such as clippy 0.0.212 (4e7e71b 2019-10-11) don't have this lint, so it's hard to pin down.

[taiki-e]

A workaround for this is to use #[allow(clippy::unused_self)] on impl block: playground