Sealed classes - would you want them in D?

[KingJoffrey]

On Tuesday, 15 May 2018 at 21:05:10 UTC, Jonathan M Davis wrote:
>
> Ultimately, if newcomers don't want to be tripped up on stuff 
> like this, their best bet is probably to read books like 
> Andrei's "The D Programming Language" and Ali's "Programming in 
> D."
>

"The unit of object encapsulation in D is the class." - page 175, 
The D Programming Language, 2010, Andrei Alexandrescu.

What it really should have included, locally, within that same 
section, is the implications of this 'encapsulation' with regards 
to how 'facebook like friendship' is a core design component of 
the D module.

i.e, on the next line, Andrei could have continued..

"However, if your class is contained within a module, then this 
encapsulation barrier kinda breaks down, because everything in 
the module becomes a friend of that class, whether you like it or 
not. You have no say in the matter. If you don't like it, fine, 
but that's how D does things, so just be careful what you put in 
a module".