Proper way to handle "alias this" deprecation for classes

[Salih Dincer]

On Wednesday, 17 May 2023 at 08:00:17 UTC, Dom DiSc wrote:
> If you want auto-conversion, you should be more explicit:
> ```d
> float opCast() { }
> ```
> because if you return "auto" it is not the highest-prio fit and 
> therefore not chosen.
> If you have multiple choices, you still don't need to use 
> "auto". Instead you can return T:
> ```d
> T opCast(T)() if(isFloatingPoint!T)
> {
>    return cast(T)num / cast(T)den; // float, double or real
> }
> ```
> Kind of ironic, but especially "auto" does NOT fit 
> automatically :-)

Sorry for not expressing myself better.  Let me try to explain 
with another example:

```d
struct RightShift
{
   int num, shr;

   T opCast(T : char)()
    => cast(T)(num >> shr);
}
import std.stdio;
void main()
{
   auto f = RightShift(128, 2);
   char chr = cast(char)f | '\1';
   assert(chr == '!');
   
   //char test = f; // Error: cannot implicitly convert expression
   //assert(test == ' '); // `f` of type `RightShift` to `char`
}
```

This snippet works fine.  But hidden the code gives an error.  
The reason is that the compiler ignores the explicitly specified 
lines without using auto.

SDB at 79