Set<String> (@NotNull StubElement<?> stub) { Set<String> result = null; while (stub != null) { Set<String> names = getOwnTypeParameterNames(stub); if (!names.isEmpty()) { if (result == null) result = new HashSet<>(); result.addAll(names); } if (isStatic(stub)) break; stub = stub.getParentStub(); } return result == null ? Collections.emptySet() : result; }