I don't mind Java checked exceptions but of the languages in this style I think I prefer C#'s Task type. It combines a promise with a simple IsFaulted boolean

I don't mind Java checked exceptions but of the languages in this style I think I prefer C#'s Task type. It combines a promise with a simple IsFaulted boolean and a way to rethrow the caught exception at your discretion (or it will throw if you accidentally access the result getter). You can use catch block style with typed exception handling or simple boolean checks depending on the situation and what you prefer.