boolean (@NotNull ULiteralExpression expr) { if (!expr.isString()) return false; PsiElement sourcePsi = expr.getSourcePsi(); if (sourcePsi == null) return false; final IProperty property = sourcePsi.getUserData(CACHE); if (property == NULL) return false; if (property != null) return true; final boolean isI18n = JavaI18nUtil.mustBePropertyKey(expr, null); if (!isI18n) { sourcePsi.putUserData(CACHE, NULL); } return isI18n; }