private @Nullable List<LookupElement> addShorterElements(@Nullable Collection<LookupElement> from) {
          List<LookupElement> toLift = null;
          if (from == null) {
            return null;
          }

          if (arraysProcessed.add(from)) {
            for (LookupElement shorterElement : from) {
              if (mySrcSet.contains(shorterElement) && processed.add(shorterElement)) {
                if (toLift == null) {
                  toLift = new ArrayList<>();
                }
                toLift.add(shorterElement);
              }
            }
          }
          return toLift;
        }
private @Nullable List<LookupElement> addShorterElements(@Nullable Collection<LookupElement> from)