I know this is going to sound trite, but “don’t do that”. It’s no different than deciding to poll the win32 event queue inside an a method you executed in response to polling the event queue. Nested shit is always going to cause a bug. I guess each new generation just has to learn.
Don't do ... what, exactly? The RFD answers this more precisely and provides suggestions for alternatives. But it's not very simple because the things that can cause this are all common patterns individually and it's only the confluence (which can be spread across layers of the program) that introduces this problem. In our case, it wasn't a Mutex, but an mpsc channel (that was working correctly! it just got very briefly saturated) and it was 3-4 modules lower in the stack than the code with the `tokio::select!` that induced this.
It’s not nested, that’s the thing.