Why dtor are not executed when removing a struct from associative arrays?

[Tejas]

On Monday, 20 September 2021 at 18:13:53 UTC, Steven 
Schveighoffer wrote:
> On 9/20/21 10:22 AM, Tejas wrote:
>> In case you still want to delete stuff deterministically 
>> despite what Steve said, I suggest you make your `struct` a 
>> reference and use `core.memory.__delete`(not recommended to 
>> use this carelessly, btw)
>
> Do not call `__delete` here, use `destroy`. `__delete` will 
> attempt to deallocate the block, which likely will fail since 
> the key comes before the value, and GC.free on an interior 
> pointer (I think) fails.
>
> But if it succeeded, it would not be good. This leaves a 
> dangling pointer inside the AA. Rehashing the AA likely would 
> result in a memory corruption.
>
> If you use destroy, the destructor will be called by the GC as 
> well, but a struct should properly handle destroying the .init 
> value.
>
> -Steve

It doesn't succeed when object is stack allocated, otherwise it 
works; that's why I suggested changing `S` to `S*`.

As for why I didn't use `destroy`, I assumed OP wanted to free 
the memory. If they just want the destructor to run, then 
`destroy` is better(and safer).

(Also, `hashOf` seems to work just fine even after using 
`__delete`, not that it means using `__delete` should ever be 
recommended over using `destroy`)

```d
import std.stdio;
import core.memory:__delete;

struct S
{
	int a;
	this(int param){
		a = param;
	}
	~this()
	{
	    writeln("S(",a,") is being destructed");
	}
}

void absoluteRemove(AA, keyType)(AA assArray, keyType key){
	//assArray.remove(key);
	__delete(assArray[key]);
}


void main()
{
	S*[int] aa;
         aa[1]  = new S(5);
         absoluteRemove(aa, 1);
         writeln(aa.hashOf);
         aa[2] = new S(10);
         writeln(aa.hashOf);
         absoluteRemove(aa, 2);
         writeln(aa.hashOf);
         writeln("Why no dtor call on remove?");
}



Output:
S(5) is being destructed
2451737883
5104465521
S(10) is being destructed
5378492086
Why no dtor call on remove?
```