Collection<TypeMigrationUsageInfo> () { final Set<TypeMigrationUsageInfo> infos = new HashSet<>(); for (Map.Entry<TypeMigrationUsageInfo, HashSet<Pair<TypeMigrationUsageInfo, PsiType>>> entry : myRootsTree.entrySet()) { infos.add(entry.getKey()); infos.addAll(ContainerUtil.map(entry.getValue(), pair -> pair.getFirst())); } return infos; }