Hi,

Not sure if this is right place to ask question, please excuse me if I am at wrong place. I am relatively new to Rust and am trying to understand some intricacies of the language.

I was reading through the code and am curious if we need the following,

unsafe impl<M: Send + Sync> Sync for Runnable<M> {}

Why can't it just be

unsafe impl<M: Sync> Sync for Runnable<M> {}

As per my understanding, even if M is not Send, the Task and Runnable can still be safely shared across threads because there is no way to get exclusive access of metadata through their reference.