It looks complicated but if you think about it as a series of property descriptions it becomes much easier. I'm gonna make it worse first by substituting the `

It looks complicated but if you think about it as a series of property descriptions it becomes much easier. I'm gonna make it worse first by substituting the `BoxFuture` type alias with its definition but that makes it easier to explain. future: Mutex<Option<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>>, What this means is that the future field stores something that is a: - Dynamically dispatched object (with a V-Table) that implements methods from the Future trait, and returns nothing () = void. (dyn Future<Output = ()>) - That thing needs to be sendable between Threads (+ Send) - And must potentially live forever (+ 'static) - The dynamic dispatch stuff only works with heap allocations because the V-Table pointer is stored in the double wide smart-pointer. In this case we use a Box which means only one thing/thread can hold it at a time (unlike reference counted Rc/Arc). - That allocation of the Heap allocation must not be moved around in memory. (Pin<...>) - that thing might not be there (it can be Null), but replacing/taking/putting the thing will be secured by the mutex so that's a nice guarantee for multithreading (Option<...>) - access to a thing is synchronised via a mutex (Mutex<...>) So while it looks horrible at first sight, it is simply telling you a lot about the guarantees of that particular type.