#![feature(async_await)]

use std::boxed::Box;
use std::future::Future;
use std::pin::Pin;

pub type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;

pub trait Queue<'a> {
    type ResultFut: Future<Output = ()> + 'a;

    fn store(&'a mut self, a: &'a str) -> Self::ResultFut;
}

struct MyQueue {
}

impl<'a> Queue<'a> for MyQueue {
    type ResultFut = BoxFuture<'a, ()>;

    fn store(&'a mut self, a: &'a str) -> Self::ResultFut {
        Box::pin(async {
            println!("A is {}", a);
        })
    }
}