Why is Task not co-variant?

by

According to someone who may be in the know…

The justification is that the advantage of covariance is outweighed by
the disadvantage of clutter (i.e. everyone would have to make a
decision about whether to use Task or ITask in every single
place in their code).

It sounds to me like there is not a very compelling motivation either way. ITask<out T> would require a lot of new overloads, probably quite a bit under the hood (I cannot attest to how the actual base class is implemented or how special it is compared to a naive implementation) but way more in the form of these linq-like extension methods.

Somebody else made a good point – the time would be better spent making classes covariant and contravariant. I don’t know how hard that would be, but that sounds like a better use of time to me.

On the other hand, somebody mentioned that it would be very cool to have a real yield return like feature available in an async method. I mean, without sleight of hand.

More Related Contents:

  1. Convert List to List
  2. ‘await’ works, but calling task.Result hangs/deadlocks
  3. How do I abort/cancel TPL Tasks?
  4. How is Generic Covariance & Contra-variance Implemented in C# 4.0?
  5. Have a set of Tasks with only X running at a time
  6. How can I call an async method in Main?
  7. vs in Generics
  8. C#: Overriding return types
  9. Set ApartmentState on a Task
  10. c# covariant return types utilizing generics
  11. covariance in c#
  12. async Task vs async void
  13. Why cannot IEnumerable be cast as IEnumerable?
  14. Contravariance explained
  15. How can I prevent synchronous continuations on a Task?
  16. T must be contravariantly valid
  17. Run work on specific thread
  18. Why can’t I cast from a List to List?
  19. Why does C#/CLR not support method override co/contra-variance?
  20. Why does C# (4.0) not allow co- and contravariance in generic class types?
  21. What happens while waiting on a Task’s Result?
  22. How to get around lack of covariance with IReadOnlyDictionary?
  23. Thread.Sleep vs Task.Delay?
  24. Is this a covariance bug in C# 4?
  25. How to handle Task.Run Exception
  26. Task.Run with Parameter(s)?
  27. Await vs Task.Result in an Async Method [duplicate]
  28. Understanding Covariance and Contravariance in C# 4.0
  29. c# 9.0 covariant return types and interfaces
  30. caching the result from a [n async] factory method iff it doesn’t throw

Leave a Comment