Adds type hints to `empty`, `never` and `failWith`.
Adds type hints to `empty`, `never` and `failWith`.

kzaher/RxSwift,ReactiveX/RxSwift,petester42/RxSwift,cfraz89/RxSwift,kzaher/RxSwift,cfraz89/RxSwift,shiratsu/RxSwift,tottakai/RxSwift,KyoheiG3/RxSwift,shiratsu/RxSwift,KyoheiG3/RxSwift,cfraz89/RxSwift,petester42/RxSwift,ashfurrow/RxSwift,tottakai/RxSwift,ashfurrow/RxSwift,thanegill/RxSwift,ashfurrow/RxSwift,thanegill/RxSwift,hsoi/RxSwift,hsoi/RxSwift,hsoi/RxSwift,hsoi/RxSwift,KyoheiG3/RxSwift,cfraz89/RxSwift,petester42/RxSwift,shiratsu/RxSwift,thanegill/RxSwift,kzaher/RxSwift,thanegill/RxSwift,ReactiveX/RxSwift,petester42/RxSwift,tottakai/RxSwift,ashfurrow/RxSwift,kzaher/RxSwift,ReactiveX/RxSwift