#![feature(coverage_attribute)] #![feature(noop_waker)] // edition: 2021 fn main() { for i in 0..16 { let future = async { if i >= 12 { println!("big"); } else { println!("small"); } }; executor::block_on(future); } } mod executor { use core::future::Future; use core::pin::pin; use core::task::{Context, Poll, Waker}; #[coverage(off)] pub fn block_on(mut future: F) -> F::Output { let mut future = pin!(future); let mut context = Context::from_waker(Waker::noop()); loop { if let Poll::Ready(val) = future.as_mut().poll(&mut context) { break val; } } } }