Enumerator#rewind

static VALUE
enumerator_rewind(VALUE obj)
{
    struct enumerator *e = enumerator_ptr(obj);

    rb_check_frozen(obj);

    rb_check_funcall(e->obj, id_rewind, 0, 0);

    e->fib = 0;
    e->dst = Qnil;
    e->lookahead = Qundef;
    e->feedvalue = Qundef;
    e->stop_exc = Qfalse;
    return obj;
}