Unclear if AtomicBool implements Send

[tbelaire]

I was looking through all the types, seeing how Send and Sync bounds relate to each other, when I noticed that unlike most other types in sync, in the impl section AtomicBool only says

impl Sync for AtomicBool

without any mention of Send, one way or the other.

I was expecting that like Arc, Cell, and Mutex, there would be an explicit listing of it's Sendness and Syncness.

[retep998]

Send and Sync only need to be explicitly implemented when they want to be Send and Sync in cases where they wouldn't automatically be Send and Sync. This is either closely related to or a duplicate of #17606

[apasel422]

Closing as duplicate.