Why allow initializers of non-static members that allocate?

[Arafel]

On 10/6/22 14:58, Salih Dincer wrote:
> On Friday, 10 June 2022 at 07:35:17 UTC, Bastiaan Veelo wrote:
>> I have been foolish enough to make a mistake like this:
>> ```d
>> struct S
>> {
>>     int[] arr = new int[](5);
>> }
>> ```
> 
> Well, if the b's may not be equal, there's a simple solution. But why 
> are a's like that, they're not static!
> 
> ```d
> void main()
> {
>    struct S(size_t size)
>    {
>      int[] arr = new int[size];
>    }
> 
>    S!5 a1, a2;
>    assert(a1.arr.ptr == a2.arr.ptr);
> 
>    S!5 b1;
>    S!6 b2;
>    assert(b1.arr.ptr != b2.arr.ptr);
> }
> ```
> SDB at 79

Because the `arr` are created for each instantiation of the template.

All S!5 share one default value, so you could also:

```d
assert (a1.arr.ptr == b1.arr.ptr);
```

However, S!6 becomes a completely different struct, and thus gets a 
different default `arr`.

Note that this would also happen with static members:

```d
struct S(int T) {
     static int foo;
}

static assert(&S!1.foo !is &S!2.foo);

void main() { }
```