Constant delegation

[vic1707]

fixes: #79

Hi, I think I got it working 😁.
Let me know if anything needs to be changed, if you have other test suggestions or a better documentation !

[vic1707]

I decided to generate the constant getter for each match arm since it's a const fn and will get optimized out by the compiler.
This helped keep the codegen centralized.

Another approach that could work would be to generate the getter once before the match statement.
If you prefer the later tell me and I'll make the changes 🙃

[Kobzol]

Thanks! The implementation looks pretty good. Left a few nits, but otherwise it's close to being ready I think.

I decided to generate the constant getter for each match arm since it's a const fn and will get optimized out by the compiler.

This is fine, we should generate the function locally, so that e.g. this works:

#[test]
fn multiple_consts() {
    trait Foo {
        const A: u32;
        const B: u32;
    }

    struct A;
    impl Foo for A {
        const A: u32 = 0;
        const B: u32 = 0;
    }

    struct Wrapper(A);
    impl Wrapper {
        delegate! {
            to &self.0 {
                #[const(Foo::A)]
                fn a(&self) -> u32;

                #[const(Foo::B)]
                fn b(&self) -> u32;
            }
        }
    }
}

Could you please add the above as a test? Thanks!

[vic1707]

Thanks for the review, PR updated, let me know if I forgot something (in which case I'm sorry 😅)

[Kobzol]

I think that you forgot an empty comment on one line. Once you remove it, please squash the commits into one and we're good to go :)

[Kobzol]

Forgotten line? :)

[vic1707]

Crap it was my marker for where I could inject the constant getter if you asked for it 🤣😅

[Kobzol]

Reformatting is also needed (see CI).

[vic1707]

should be good 👍

[Kobzol]

Thanks! Could you please squash the commits now?

[vic1707]

done ✅

[Kobzol]

Thank you! :)