}
    }

    private void collectAll() {
        while (!uncollected.isEmpty()) {
            MacroSource source = uncollected.removeFirst();
            source.collectInto(this);
        }
    }

    interface MacroSource {
        void collectInto(CollectingMacroLookup lookup);
    }

            ImmutableList.Builder<T> builder = ImmutableList.builder();
            // Collect elements discarding potential side effects aggregated in the returned value
            collector.collectInto(builder);
            List<T> realized = builder.build();
            for (T element : realized) {
                doAddRealized(element);
            }
        }
    }