Changing the tree structure to make it easier to delete.
Making one as you go.
First assume that you have a parent pointer.
An unfortunate error code collision, but the explanatory text leads the way.
You don't have to understand it, but you should be able to extract data from it.
It used to be there because PropertyValue started out as the fundamental variant type before shifting focus to being the fundamental boxed type.
If all you're doing is setting properties, you can do it any way you like.
cheap_steady_clock faster than std::chrono::high_resolution_clock ?
It's quite a bit faster, though maybe you don't care.
If the callback requires copyability.
It's more important to clean up when you leave.