alias this and opDot()

[user1234]

On Wednesday, 28 September 2022 at 03:45:59 UTC, Salih Dincer 
wrote:
> Ok, opDot() is deprecated in version 2.082. However, if we 
> simulate this situation with a function (opdot in our example), 
> we get unexpected results.
>
> ```d
> struct Point { int x, y; }
>
> struct S
> {
>     Point point;
>     alias opdot this;
>
>     auto opdot()
>     { // opDot() is deprecated in v2.082
>       //this.point = Point(100, 100);/* <-- also if you only 
> use: s == Point(100, 101)
>         point.x = 100;
>         point.y = 100;
>         point.x++;//*/
>
>         return &point;
>     }
> }
>
> void main()
> {
>     S s;
>     s.x++; // as if this line doesn't exist!
>     s.y++;
>
>     //s.x++; //  <-- also if you use: s == Point(102, 100)
>     assert(s.point == Point(101, 101));
> }
> ```
>
> SDB at 79

opdot is called two times so you reset the state of point members 
100

```d
struct Point { int x, y; }

struct S
{
     Point point;
     alias opdot this;

     Point* opdot() return
     {
         this.point.x = 100;
         this.point.y = 100;
         return &this.point;
     }
}

void main()
{
     S s;
     s.x += 1;
     assert(s.point == Point(101, 100));
     s.y += 1;
     assert(s.point == Point(100, 101));
}
```