throw new IllegalArgumentException("key already present: " + key);
    }

    /*
     * The ordering here is important: if we deleted the key entry and then the value entry,
     * the key entry's prev or next pointer might point to the dead value entry, and when we
     * put the new entry in the key entry's position in iteration order, it might invalidate
     * the linked list.
     */

    if (oldEntryForValue != null) {