how to have alias this with an unaccessible member?

[Simen Kjaeraas]

On Sat, 18 May 2013 01:13:00 +0200, Timothee Cour  
<thelastmammoth at gmail.com> wrote:

> How to have alias this with an unaccessible member (x below).
> Making the member private won't work as it'll disable all operations on
> said member.
>
> ----
> struct A(T){
>   T x;
>   //private T x would prevent alias this from doing anything useful
>   alias x this;
> }
> void main(){
>   auto a=A!int;
>   a++;//should do a.x++;
>   static assert(!__traits(compiles,a.x)); // I want this to hold
>
> }
> ----


The common way to do it is with a read-only property:

struct A(T) {
   private T x;

   @property
   T get() {
     return x;
   }

   alias get this;
}

void main(){
   auto a = A!int;
   a++; //should do a.x++;
   static assert(!__traits(compiles, a.x)); // This now holds!
   static assert(__traits(compiles, a.get)); // As does this, which may or  
may not be palatable. :(
}

This has been discussed numerous times before, but I believe the current  
behavior is here to stay.

-- 
Simen