Is there any good reason why C++ namespaces are "closed" in D?

[Timon Gehr]

On 27.07.2018 19:28, Atila Neves wrote:
> I understand that being able to "reopen" namespaces in C++ is 
> contentious - anybody can add to the `std` namespace in their own code. 
> D doesn't have anything like it, and instead has packages and modules. 
> So far, so good.
> 
> But why does this not compile?
> 
> extern(C++, ns) { void foo(); }
> extern(C++, ns) { void bar(); }

Both of the extern(C++, ns) declarations create a separate namespace 
declaration. (Which is needed to allow ns.foo and ns.bar respectively.)

I.e. the reason is that it was easier to implement in the compiler. 
There might be a way to add support for it by overriding overloadInsert 
in Nspace.