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

[Daniel N]

On Monday, 30 July 2018 at 08:44:14 UTC, Walter Bright wrote:
>
>   struct S1 { extern(C++, ns) void foo(); } alias foo = 
> S1.ns.foo;
>   struct S2 { extern(C++, ns) void bar(); } alias bar = 
> S2.ns.bar;
>
> Perfect!
>
>

I tried that but it mangles wrong.. it includes "S1" which is not 
what you want, so I gave up binding to C++ and used C instead.

pragma(msg, foo.mangleof);
_ZN2S12ns3fooEv

Even if it worked, you'd still see the full name in error 
messages and reflection.

It's much harder to undo parts of one complex operation, compared 
to composing two simple building blocks. Couldn't we just add a 
new parameter to control scope or add a pragma or something?