go embeddings and "public alias x this;" on a private member x

[Timothee Cour]

I'd like public alias x this to reset protection attribute on a (private)
member x:

b.d:
struct B(T){
    private T x;// would normally prevent alias this from doing anything
useful
    public alias x this;
}

a.d:
void main(){
    auto a=B!int();
    a++;//should do a.x++; semantic change: even though x is private,
public alias x this should behave as if x were public.
    //a.x++ should still be compile error of course.
    static assert(!__traits(compiles,a.x)); //fails but seems like a bug; I
just reported it: 10170

}


(likewise with protected alias this, etc).

I think this makes sense:
* this allows protection (x is an implementation detail) so that 'this'
behaves exactly as 'x'
* also, without this change of behavior, "alias x this" would not make much
sense in terms of behavior outside the class (inside behavior should just
access x directly)

Then, when multiple alias this statements will become allowed in D (will
it?), we would have implemented something similar to go "embeddings" in GO
(see http://golang.org/doc/effective_go.html)

(note, I posted an earlier form of this in
http://forum.dlang.org/post/mailman.97.1369373126.13711.digitalmars-d-learn@puremagic.com
)
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