For procedural code, async is fine. I still hate writing anything resembling a higher-order function (a function that takes or returns a function) in async Rust

For procedural code, async is fine. I still hate writing anything resembling a higher-order function (a function that takes or returns a function) in async Rust. The type constraints become longer than the code, and I can never seem to remember what I need to pin, unpin or box.