Delegates with stackpointers

[Alex]

On Saturday, 29 September 2018 at 06:01:50 UTC, Ritchie wrote:
> How does a delegate with a stackpointer work? e.g. in this 
> example:
>
> https://run.dlang.io/is/XviMSl
>
> Does the second call to foo not overwrite the stack of the 
> first call and thereby the data pointed to by bar1? How is that 
> data preserved?

Why should a call to foo overwrite something? Aren't these two 
foos equivalent from this point of view?

´´´
DelegateT foo1() {
     int a = 0;
     void bar() {
         a++;
         writeln(a);
     }
     return &bar;
}

auto foo2()
{
     struct S
     {
         int a;
         void opCall()
         {
             a++;
             writeln(a);
         }
     }
     return S.init;
}
´´´