I have thought about creating a template struct with a single member that blows up if you try to insert null. Something like this:
public struct NotNull<T>
{
private readonly T val;
public T Value {
get { return val; }
}
public NotNull(T v)
{
if (v==null)
throw new Exception();
val = v;
}
}
However you can still create a class FOO with a member NotNull<T> xxx and xxx may be entirely uninitialized. It can be then passed from one method to another until you try to read it, so it basically does not give any guarantees.
I thinks this is why they pulled non-nullable types from C# - they couldn't figure out what to do in this case. If I were them I would force the constructor of FOO to blow up on exit if xxx is not populated. That would help a little bit. Although it still causes problems if a method is invoked from the constructor.
So yeah, it's a tough problem. Maybe they could add a check when a field of type NotNull<T> is read to throw an exception? That way you're still possibly in trouble when reading a field, but at least you can be confident that if you receive a method parameter NotNull<T> you know it's not null.
