type Link<K> = Option<Weak<Mutex<LruNode<K>>>>;
Weak pointer to a LruNode, used to connect nodes in the doubly-linked list. The strong reference is guaranteed to be stored in the data map of the LruQueue.
LruNode
data
LruQueue
enum Link<K> { None, Some(Weak<Mutex<RawMutex, LruNode<K>>>), }
No value.
Some value of type T.
T