warn_self_convention and copy?

[wackywendell]

I recently got a warn_self_convention lint on a type that implements Copy, something like this:

#[derive(Copy)]
pub struct Color(pub u8, pub u8, pub u8);

impl Color {
    /// Convert to a 3-tuple, from 0 to 1
    pub fn as_floats(self) -> (f32, f32, f32) {
        let Color(r,g,b) = self;
        (
            (r as f32) / (u8::max_value() as f32),
            (g as f32) / (u8::max_value() as f32),
            (b as f32) / (u8::max_value() as f32),
        )
    }

src/palette.rs:43:22: 43:30 warning: methods called `as_*` usually take self by reference; consider choosing a less ambiguous name, #[warn(wrong_self_convention)] on by default
src/palette.rs:43     pub fn as_floats(self) -> (f32, f32, f32) {

It seems to me that types that implement Copy should be permitted to use pass-by-value instead of pass-by-reference for as_, to_, and other such methods.

[birkenfeld]

Agree. I'll see how easy it is to fix this.

[llogiq]

Good catch! It should be possible to check if the Self type binds to Copy by checking the trait bounds.

[birkenfeld]

Please check if it works with this PR applied.

[wackywendell]

Yes, it does! Nice work!