Private visible?

[Walter Bright]

Ivan Senji wrote:
> Various 'poisoning' techniques sound a lot like C++ to me. There one can 
> make classes that can not be constructed, can not be inherited from, can 
> not be passed by value, cannot be allocated on stack and many different 
> things by making something that is private. But are these techniques 
> realistic or even possible in D?

Sometimes it is valuable to be able to say "you can't do this operation 
with this type". I don't see why this ability should be restricted to C++.