DIP1000

[ag0aep6g]

On Thursday, 23 June 2022 at 16:08:01 UTC, Ola Fosheim Grøstad 
wrote:
> How am I supposed to write this:
>
> ```d
> import std;
> @safe:
>
> struct node {
>     node* next;
> }
>
> auto connect(scope node* a, scope node* b)
> {
>     a.next = b;
> }
>
> void main()
> {
>     node x;
>     node y;
>     connect(&x,&y);
> }
>
> ```
>
>> Error: scope variable `b` assigned to non-scope `(*a).next`

DMD accepts this:

```d
@safe:

struct node {
     node* next;
}

void connect(ref scope node a, return scope node* b)
{
     a.next = b;
}

void main()
{
     node y;
     scope node x;
     connect(x, &y);
}
```

But that only works for this very special case. It falls apart 
when you try to add a third node. As far as I understand, `scope` 
cannot handle linked lists. A `scope` pointer cannot point to 
another `scope` pointer.

So as to how you're supposed to do it: with @system.