Implicit cast from OneOf<> to Task<OneOf<>>

[amir734jj]

We are using Task<OneOf<>> frequently in our codebase and I wish there was a way to add this implicit cast from OneOf<> to Task<OneOf<>> but we C# doesn't allow adding implicit casts outside of declaring class (i.e. OneOf<>). This is because we have a use case where we use .Switch and in one branch of OneOf we run an async lambda and in the second branch of OneOf we run a sync operation just returning the result. We can use Task.FromResult in the second lambda but I just wish there was a implicit cast from OneOf of anything to Task<OneOf>

public static implicit operator Task<OneOf<T0>>(OneOf<T0> t) => Task.FromResult(t);

[Foxtrek64]

I disagree that this should be an implicit cast. In my opinion, implicit casts should be reserved for when a particular thing and a particular other thing are synonymous in some manner, and it should always be from more specific to less specific (e.g. a name object which contains first + last may be implicitly cast to string).

I would argue that OneOf<T0> and Task<OneOf<T0>> are not the same - the former is a value container and the latter is the promise of a value container. Additionally, we're moving from less specific to more specific.

If we were to add this, I think my preferred form would either be an explicit operator or, perhaps better, AsTask() or AsValueTask() extensions.

Something like this, either as a member or an extension method.

public Task<OneOf<T0>> AsTask(OneOf<T0> oneOf) => Task.FromResult(oneOf);
public Task<OneOf<T0>> AsTask(Func<OneOf<T0>> factory) => Task.FromResult(factory.Invoke());