GATs allow traits to abstract over associated types that are themselves to some degree abstract. In this case, it's necessary to do the relevant trait machinery around lifetime transformation since we need to be able to talk about "a replaceable lifetime of a type" in a generic way.
GATs allow traits to abstract over associated types that are themselves to some degree abstract. In this case, it's necessary to do the relevant trait machinery around lifetime transformation since we need to be able to talk about "a replaceable lifetime of a type" in a generic way.