How do I specify that a Func object doesn't return null with JetBrains annotations?

问题

I have a bit of code:

public void Foo([NotNull] Func<string> bar)
{
    //whatever
}

My problem is, the [NotNull] annotation is specifying that bar itself is not null. I'm looking instead for an annotation that says that the thing RETURNED BY BAR is not null.

I expected that this was possible but it doesn't seem to be. They support ItemNotNull for IEnumerables so I don't see why we can't have ReturnsNotNull for Func objects.

Am I just missing something obvious here? Surely something this basic is supported.

来源：https://stackoverflow.com/questions/35091582/how-do-i-specify-that-a-func-object-doesnt-return-null-with-jetbrains-annotatio