Avoiding default generic types, and allocator awareness

[helxi]

On Saturday, 30 December 2017 at 15:00:32 UTC, helxi wrote:
> As an exercise in http://ddili.org/ders/d.en/pointers.html, I 
> was implementing a very stripped down version of singly linked 
> list like below:
> struct Node(T)
> {
>     T item;
>     Node!T* next_item;
> }
>
> [...]

Correction, I meant:
If I leave the signature like
> these, is it actually going to affect the structure in anyway?:
> void push_front(T, N)(ref Forward_List!(T, N) list, T item);
> string to_string(T, N)(ref Forward_List!(T, N) list);