On Thu, Jul 18, 2024 at 10:13 AM Frederick Virchanza Gotham wrote:
>
> Widget foo(int const i)
> {
> return construct_modify<Widget>(
> i,
> [](auto &a) -> bool { return a.some_observer; },
> [](auto &a) -> Widget { return Widget(0); }
> );
> }


Correction, that should be:

   Widget foo(int const i)
   {
     return construct_modify<Widget>(
         i,
         [](auto &a) -> bool { return a.some_observer(); },
         [](void ) -> Widget { return Widget(0); }
     );
   }