Difference with other "delegate" crates.

[bragov4ik]

I stumbled upon this crate and I think it would be nice to have this written down somewhere. I think the list should simplify choosing between the crates & better understand the aim of this crate.

In particular, in discussions about rust delegate rfc's I found delegate and ambassador.

So, the question is: what are the features that are unique to this crate?

[bragov4ik]

I discovered one use case this crate excels at. Apparently, other crates cannot elegantly delegate associated methods to some other type. For example, the following trait delegate implementations benefit from portrait:

trait SomeTrait {
    fn foo() -> i32;
    fn baz();
}

• ambassador does not support methods without receiver
• delegate does not instrument the trait, so implementations have to list all trait methods (which kinda defeats the purpose of macro: getting rid of code duplication)

So, portrait can solve such use case easily:

struct BaseCase;

impl SomeTrait for BaseCase {
    fn foo() -> i32 { 123 }
    fn baz() {
        println!("Hello, World!");
    }
}

struct Wrapper<T: SomeTrait>(PhantomData<T>);

#[portrait::fill(portrait::delegate(T))]
impl<T: SomeTrait> SomeTrait for Wrapper<T> { }

Thanks for making this crate; now my inner perfectionist is happy 🎉

[SOF3]

portrait is actually a framework for exposing trait body to proc macros, which includes other fillers like default and log. I added delegate simply because it happens to fit in the framework as well; didn't really do research on other delegation crates in the ecosystem. But much thanks for the comparison!