ambassador 0.5.1

Trait implementation delegation via procedural macros
Documentation 
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extern crate ambassador;

use ambassador::{delegatable_trait, Delegate};

#[delegatable_trait]
pub trait Shout {
    fn shout(&self, input: &str) -> String;
}

pub struct Cat;

impl Shout for Cat {
    fn shout(&self, input: &str) -> String {
        format!("{} - meow!", input)
    }
}

pub struct Dog;

impl Shout for Dog {
    fn shout(&self, input: &str) -> String {
        format!("{} - wuff!", input)
    }
}

#[derive(Delegate)]
#[delegate(Shout)]
pub enum Either<A: Shout, B: Shout> {
    Left(A),
    Right(B),
}

pub fn main() {
    let foo_animal = Either::Left::<Cat, Dog>(Cat);
    println!("{}", foo_animal.shout("BAR"));
    let bar_animal = Either::Right::<Cat, Dog>(Dog);
    println!("{}", bar_animal.shout("BAR"));
}