public static boolean isI18nProperty(@NotNull UInjectionHost 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;
  }
public static boolean isI18nProperty(@NotNull UInjectionHost expr)