void trailing() {
    Str string = {
        StrBuf tmp;
        for (Nat i = 0; i < 10; i++) {
            tmp << if (i > 0) { ", "; } else { ""; };
            tmp << i;
        }
        tmp.toS();
    };
    // "tmp" is no longer accessible.
    print(string.toS);
}
