【Rust】coroutineを使いたい

#![feature(coroutines)]
#![feature(coroutine_trait)]
#![feature(stmt_expr_attributes)]

use std::ops::{Coroutine, CoroutineState};
use std::pin::Pin;

fn main() {
    let mut coroutine = #[coroutine] || {
        yield 1;
        "foo"
    };

    match Pin::new(&mut coroutine).resume(()) {
        CoroutineState::Yielded(1) => {
            println!("yielded test");
        }
        _ => panic!("unexpected return from resume"),
    }
    match Pin::new(&mut coroutine).resume(()) {
        CoroutineState::Complete("foo") => {
            println!("foo test");
        }
        _ => panic!("unexpected return from resume"),
    }
}

error[E0554]: `#![feature]` may not be used on the stable release channel
…

$ rustup install nightly
$ cargo +nightly run
Compiling parallel v0.1.0 (/home/vagrant/dev/rust/parallel)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.28s
Running `target/debug/parallel`
yielded test
foo test

use std::ops::{Coroutine, CoroutineState};
use std::pin::Pin;

fn main() {
    let mut coroutine = #[coroutine] || {
        println!("2");
        yield;
        println!("4");
    };

    println!("1");
    Pin::new(&mut coroutine).resume(());
    println!("3");
    Pin::new(&mut coroutine).resume(());
    println!("5");
}

Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.27s
Running `target/debug/parallel`
1
2
3
4
5

Pin::new(&mut coroutine).resume(());で一旦停止するのか…