pub trait ObserverUpgradesToSelf { }Expand description
To mark types that upgrade to themselves when used as a destination in an Observables subscribe method. Usually subscribers fall into this category as they are already subscribers, so there’s no need for an upgrade. But there are a few regular observers too that chose to implement SubscriptionLike to implement a unique behavior. These observers take it upon themselves to manage their own closing logic, and maintain a teardown for added teardowns. For example, the PrintObserver does this to be able to print when it got unsubscribed, and the MockObserver to be able to track all notifications for assertions.