Derive Macro ToOutput 

#[derive(ToOutput)]
{
    // Attributes available to this derive:
    #[rainbow]
}

use object_rainbow::{InlineOutput, ToOutput};

#[derive(ToOutput)]
struct Three<A, B, C> {
    a: A,
    b: B,
    c: C,
}

object_rainbow::assert_impl!(
    impl<A, B, C> ToOutput for Three<A, B, C>
    where
        A: InlineOutput,
        B: InlineOutput,
        C: ToOutput,
    {}
);