Desire to build a clean API will stashing away resources for later use...

gistfile1.txt

struct Provider<A> {
  api: A,
  tracked_resources: TrackedResources,
}

struct Api { ...};

impl Api {
   fn create_thing() -> ThingBuilder {...}
}

impl Deref for Provider<A> {
  type Target = A
  ...
}

impl DerefMut for Provider<A> {
  ...
}

fn main() {
  let api = ...;
  let provider = Provider::new(api);
  
  let thing: Arc<Thing> = provider.create_thing().foo(1).bar("yay!").build();
  // At this point, it would be nice if provider.tracked_resources contained an Arc<Thing> in its collection... 
}