Multiple alias this, what's the hold up?

[Timon Gehr]

On 17.06.19 15:48, Mike Franklin wrote:
> void main()
> {
>      S s;
>      s = 1;
>      int i = s;  // No way to make this work in the library.  We need 
> `opAssignRight`.
> }
> ```
> ...

This is not an assignment. It is an initialization. opAssignRight would 
do nothing for this case.

> I think if we had an `opAssignRight` feature (with friends) we could 
> move the entire implementation of `alias this` to the library.

I don't think that works. (And I don't necessarily agree that it is 
desirable. See Ethan's excellent post noting issues with compile times.)

This is another case you can't do in the library right now:

struct S{
     int x;
     alias x this;
}

int foo(int x){
     return x;
}

void main(){
     import std.stdio;
     writeln(foo(S(3)));
}