Allow default constructors for structs

[Salih Dincer]

On Thursday, 29 August 2024 at 14:28:09 UTC, Ogi wrote:

> A struct with a default constructor can only be instantiated by 
> an implicit constructor call, following the same rules as a 
> struct with a disabled default constructor.

I think everything is consistent and works as it should. D gives 
more than C...

```d
struct S(T)
{
   T i;
   this(T value)
   {
     i = value;
   }
   alias i this;
}

alias sint = S!int;
void main()
{
   sint s1;
   auto s2 = sint(1);
   auto sarr= [sint(2)]; // i = 2

   sarr ~= s2; // i = 1
   sarr ~= s1; // i = 0

   assert(sarr == [2, 1, 0]);
}
```

SDB at 79