Collections question

[Tobias Pankrath via Digitalmars-d]

On Friday, 27 November 2015 at 20:14:21 UTC, Andrei Alexandrescu 
wrote:
> There's this oddity of built-in hash tables: a reference to a 
> non-empty hash table can be copied and then both references 
> refer to the same hash table object. However, if the hash table 
> is null, copying the reference won't track the same object 
> later on.
>
> Fast-forward to general collections. [...]
>
> Andrei

I'd prefer the factory method and we shouldn't allow lazy 
initialization. That's only confusing, if it sometimes works and 
sometimes won't work. Null container should throw.