Null references redux

[Walter Bright]

Justin Johansson wrote:
> Walter, in the heat of this thread I hope you haven't missed the correlation with discussion
> on "Dispatching on a variant" and noting:

Thanks for pointing it out. The facilities in D enable one to construct 
a non-nullable type, and they are appropriate for many designs. I just 
don't see them as a replacement for *all* reference types.