A cell whose value can only be accessed by a owning thread. Much like a Mutex but without blocking locks and guards. Access to ThreadCells is passed cooperatively between threads.
A ThreadCell and references therof can always be send to other threads
Threads that do not own a ThreadCell and access its value will panic. There are 'try_*' variants in the API that will not panic but return a bool or Option instead.
ThreadCell<RefCell<T>>
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