Nullable or Optional? Or something else?

[grauzone]

Andrei Alexandrescu wrote:
> I plan to add a Nullable struct to Phobos (akin to C#'s Nullable, 
> Boost's Optional).
> 
> Apparently a good design is to define Optional!T with a minimum of 
> member functions (ideally none) and have it use the "alias this" feature 
> to masquerade as a T. That way Optional!T looks and feels much like a T, 
> except that it supports a function

I still don't understand how one can feel comfortable with the fact, 
that "alias this" can overshadow arbitrary members of the alias'ed type.

Am I missing something?

> bool isNull(T)(Optional!T value);
> 
> Am I on the right track? If so, what is the name you'd prefer for this 
> artifact?
> 
> 
> Andrei