Using .require for struct types

[Salih Dincer]

On Saturday, 10 September 2022 at 16:33:03 UTC, Erdem Demir wrote:
> I wish I could use ref DListOfA returnVal = .... but we can't 
> in D.
>
> Can you please suggest alternatives?

I think you should try advanced update. Your flexibility and what 
you can do are limited by your dreams. A couple delicious code:

```d
import object, std.container;

struct A
{
     double val;
     bool isBig;
}

void main()
{
     alias  DListOfA = DList!A;
     DListOfA returnVal;
     //DListOfA[string] temp;/*
     DListOfA[string] temp = [
         "a": DListOfA( A(0) )
     ];//*/
     
     auto a = A(6, true); // replacement element
     temp.update("a", {
         return DListOfA( A(0) ); // not updated: unsucceeded but 
initialized
     }, (ref DListOfA v) {
         v = DListOfA( a ); // existing v has been replaced
         returnVal = v;
         assert(returnVal.front == a);
     });
     assert(is(typeof(temp["a"]) == DList!A));
}
```
SDB at 79