Rust's futures also get this through being poll-based. You cancel a future by dropping it. Futures compose really easily, so you can combine a bunch of future

Rust's futures also get this through being poll-based. You cancel a future by dropping it. Futures compose really easily, so you can combine a bunch of futures in interesting trees of selects and joins and any that are not completed get cleaned up automatically and with little/no overhead when they go out of scope / when the task they're a part of completes. You don't think about them like separate chunks of work, you just think about them like types you can await on and yield a value, and the compiler flattens it all out into a state machine. All of the sync and composition combinators are implemented just in the traits/types of the tokio/futures libraries because the poll/waker abstraction is low level and versatile enough. As long as you don't go out of your way to write bad async code, there's no leaks for the same reasons there's no leaks in Rust code. It feels a lot like the monadic composition of Haskell even if the means it achieves it are very different.