Why async / await allows for implicit conversion from a List to IEnumerable?

Question

I\'ve just been playing around with async/await and found out something interesting. Take a look at the examples below:

// 1) ok - obvious
public Task

        

Answer 1

Task is simply not a covariant type.

Although List can be converted to IEnumerable, Task> cannot be converted to Task>. And In #4, Task.FromResult(doctors) returns Task>.

In #3, we have:

return await Task.FromResult(doctors)

Which is the same as:

return await Task.FromResult>(doctors)

Which is the same as:

List result = await Task.FromResult>(doctors);
return result;

This works because List can be converted IEnumerable.