extern(C++, ns)

[Manu via Digitalmars-d]

C++ namespacing is causing me endless, and I mean *endless* trouble.
This idea that we express the C++ namespace hierarchy in D is the main
problem.
I don't think C++ namespaces should interfere with D scoping rules, they
should be purely for mangling.
It creates a whole bundle of edge cases which either don't have work
arounds, or REALLY awkward workarounds which typically have a heavy impact
on all the regular D code that the C++ code interacts with.

Not least of which is that C++ namespaces usually span the entire project,
and in D a C++ namespace can only appear in one module ever.
Declaring symbols with the same C++ namespace in different modules leads to
multiple definition errors, and if you are super-careful to avoid those,
you gain name resolution issues in it's place.

It is also very awkward that a C++ namespace can't be the same as a top
level package name. My top level package is named the same as one of my C++
namespaces... what do I do? It gets ugly real fast.

The main problem extends from this situation:

module x.y;

extern(C++, ns) struct Y {}


module ns.m;

import x.y; // fail, the c++ namespace is already present (top level module)
import x.y : ns.Y; // fail, '.' can't appear here
import x.y : Y; // fail, not found

// This **sometimes** works, and it's very brittle
static import x.y;
alias Y = x.y.Y;


Thing is, I'm not declaring a C++ object, I'm declaring a D object, the
only thing being that struct's take care to maintain common binary layout,
and functions just mangle like C++ so that my code links. I'm in D, I'm
declaring my stuff in the D module where it should be scoped, and where
other D code should expect to find it. I don't see any point in building
the C++ hierarchy in this space. C++ namespace rules are incompatible with
D; you can litter them through C++ code, and add new symbols to C++
namespaces from anywhere... this is fundamentally incompatible with D, and
no further reasoning should be required to conclude that it can't be
reproduced, so it should be for mangling purposes only.

I have spent **days**, actually, weeks of my free time trying to make my
tiny bit of code build, and it's just nothing but trouble after trouble. I
have completely restructured my code at least 3 times to try and find a way
to make it fit together in a way that's both practical and works, but I
just can't. It always hits some brick wall somewhere.

extern(C++, NS) looks okay in isolated tests/experiments, but try and
actually use it, and you will become very frustrated.

Please, fix this. I'm almost done. I'm really struggling to keep this dream
alive.
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