public static boolean checkCyclicInheritance(Language lang) { List<Language> frontier = ModuleUtil.refsToLanguages(lang.getExtendedLanguageRefs()); ArrayList<Language> passed = new ArrayList<Language>(); while (!frontier.isEmpty()) { List<Language> newFrontier = new ArrayList<Language>(); for (Language extendedLang : frontier) { if (extendedLang == lang && lang != BootstrapLanguages.coreLanguage()) { return false; } if (!passed.contains(extendedLang)) { newFrontier.addAll(ModuleUtil.refsToLanguages(extendedLang.getExtendedLanguageRefs())); } passed.add(extendedLang); } frontier = newFrontier; } return true; }