Iterator<TypeMigrationUsageInfo> (TypeMigrationUsageInfo n) { final HashSet<Pair<TypeMigrationUsageInfo, PsiType>> rawNodes = myRootsTree.get(n); if (rawNodes == null) { return Collections.emptyIterator(); } final List<TypeMigrationUsageInfo> in = ContainerUtil.map(rawNodes, pair -> pair.getFirst()); return in.iterator(); }