I do not really have a problem with it, but am wondering just theoretically... PHPhotoLibrary's performChanges(_:completionHandler:) - https://developer.apple.com/documentation/photokit/phphotolibrary/1620743-performchanges exists. How come completionHandler closure is not declared as escaping, when changeBlock is declared as escaping? Or more general question: If I define a function with two closure parameters where the second closure is called after the first one is finished, and the first closure is escaping, does the second closure have to be escaping as well?