The language and runtime typically cooperate to provide the operational semantics that developers are looking for. The case of Objective-C is especially interesting in this regard: developers evolved a number of conventions around reference counting, because reference counting allowed for controllable, minimal latency and contributed to a snappy UI. The language gradually absorbed these conventions into the compiler, such that certain patterns of use are part of the language specification (certain method names, basically) and the ARC code is generated for developers.