opIndexUnary post in-/decrement how to ?

[Tejas]

On Wednesday, 14 July 2021 at 15:23:05 UTC, vit wrote:
> On Wednesday, 14 July 2021 at 15:19:03 UTC, vit wrote:
>
>
> ```d
> import   std.stdio;
>
> struct abc{
>     int[100] a;
>
>     struct Proxy{
>         abc* ptr;
>     	const int index;
>
>         int opUnary(string op : "++")(){
>         	return ++ptr.a[index];     //add missing ++
>         }
>     }
>
>     Proxy opIndex(int index)return{
>         return Proxy(&this, index);
>     }
> }
>
> void main (){
>     abc s;
>     s[0]++;
>     ++s[0];
> }
>
>
> ```

I tried changing ```s[0]++``` to ``` s[0] += 1```

the same lvalue problem arose :(

```

Error: `s.opIndex(0)` is not an lvalue and cannot be modified

```