Results of searching for NS_SWIFT_UNAVAILABLE
macro in iOS 9 and OS X 10.11 headers reveal some new Swift-specific APIs.
GameplayKit.framework/Headers/GKEntity.h
70: - (nullable GKComponent *)componentForClass:(Class)componentClass
NS_SWIFT_UNAVAILABLE("Exposed in Swift as componentForClass<ComponentType: GKComponent>(componentClass: ComponentType.Type) -> ComponentType?");
GameplayKit.framework/Headers/GKStateMachine.h