An async fn that you write goes through different compiler stages, from Editor - AST - HIR - MIR - Executable. This process is complex and changing all the time. My contribution to this was removing the GenFuture type, which used to be an implementation detail of async Rust. I will give a deep dive into what this was, why it had to go, and the struggles from a contributor perspective in making it go away. A journey through different workarounds that existed temporarily, and are still existing today. Apart from this, I will also highlight some very common problems that developers may run into when developing async Rust. Why the difference between async fn and fn - impl Future matters a lot. Why the mem::size_of of Futures is currently a great concern, how to work around that, as well as an outlook on the Future (pun intended) when the compiler will improve and make manual workarounds unnecessary. 🦀 *About Arpad Borsos* 🦀 (https://swatinem.de/) Hi, I’m Arpad, and I go by Swatinem online. I work with (async) Rust day-to-day, writing critical processing infrastructure at Sentry. I’m also interested in improving Rust itself, where my focus has been on improving async Rust, and some work around code coverage.