Struct template instancing inside of class failed

[Denis Feklushkin]

On Friday, 2 May 2025 at 22:51:24 UTC, monkyyy wrote:

>> I suspect that class stores template parameter "a" in some 
>> hidden fields and this behaviour impossible for POD structs?
>
> Theres allot of spooky things here

The main question for me is: why it worked for the class, but not 
for the struct?

>
> it will compile if you add static to `static int field = 123;`
>
> if you want a spooky reference to a variable

(Or function, or delegate)

> I suggest my "innate" code avoid this construction logic your 
> playing with

The whole idea looks something like this:

```d
struct S(alias outer_handler) {
     int internal_field = 1;
     this(int ctor_arg){
         internal_field = ctor_arg;
         assert(outer_handler + internal_field == 124, "ctor 
failed");
     }

     void someMethod() {
         assert(outer_handler + internal_field == 124, "method 
failed");
     }

     ~this(){
         // imitate some destruction process
         assert(outer_handler + internal_field == 124, 
"destruction failed");
     }
}

class Test {
     int field = 123;
     ref getField() => field;

     alias S_Inst = S!getField;
     S_Inst s;

     this(){
         // Error: calling non-static function `getField` requires 
an instance of type `Test`
         s = S_Inst(1);
     }
}

void main() {
     auto t = new Test;
}
```