Specifying C++ symbols in C++ namespaces

[Tove]

On Sunday, 6 April 2014 at 02:33:38 UTC, Walter Bright wrote:
> On 4/5/2014 6:26 PM, Michel Fortin wrote:
>> What if you also have a C++ foo at global scope?
>
> It'll work exactly the same as import does.
>
>
>>     module cpptest;
>>
>>     extern (C++) void foo();
>>     extern (C++, namespace = A) void foo();
>>
>>     foo(); // ambiguous
>>     A.foo(); // works
>>     .foo(); // works?
>
> Yes.
>
>>     cpptest.foo(); // works?
>
> Yes.
>
>> Does these two last lines make sense?
>
> Just as much sense as:
>
>     module bar;
>     void foo();
>     .foo(); // works
>     bar.foo(); // works
>
> Namespace lookup rules would be exactly the same as for imports 
> and mixin templates.

My main reservation against the new suggestion is that one would 
be forced to open a new nested namespace even when it's 
detrimental, because in some cases the namespace structure is 
already reflected in the filesystem(just like for D:s module 
system).

I can't assess how widespread this is globally, but at least some 
high-quality projects already have guidelines to use 
file/namespace mappings.

A random example from boost:
boost::asio::ip::multicast
boost/asio/ip/multicast.hpp

One can of course workaround this issue with an extra alias for 
every imported symbol, or use compile-time reflection to 
auto-generate all alias statements... (or heaven forbid, put 
entire boost in one file ;))

I assume the "namespace = xxx" syntax is some sort of named 
parameter, would it be possible to add another similar param, 
which only changes mangling and doesn't actually create a new 
scope?