Keyword to avoid not null references

[bearophile]

Adam D. Ruppe:
> We can do not null in the library reasonably
> well. I have a basic one in github:
>
> https://github.com/D-Programming-Language/phobos/pull/477

It says:

>I haven't actually used any NotNull in practice, but from the 
>attached tests, it looks like it will work well - hence, the 
>pull request.<

I think before putting something in Phobos it's generally better 
to have used it in Real Code for some time.

I am not sure a mostly-library-defined solution (mostly because 
@disable is a built-in) is good enough compared to a solution 
built in the type system.

I will try to use your NotNull struct.

Bye,
bearophile