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

[timotheecour]

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)