anchor.diff:  
     /**
      * Removes all elements in the list. The length of the list
  -   * becomes zero. Throws a [UnsupportedOperationException] if
  +   * becomes zero. Throws an [UnsupportedOperationException] if
      * the list is not extendable.
      */
     void clear();
  
positive.code:   /**
     * Appends all elements of the [collection] to the end of list.
     * Extends the length of the list by the length of [collection].
     * Throws a [UnsupportedOperationException] if the list is not
     * extendable.
     */
    void addAll(Collection<E> collection);
  
negative.code: 
    /**
     * Changes the length of the list. If [newLength] is greater than
     * the current [length], entries are initialized to [:null:]. Throws
     * an [UnsupportedOperationException] if the list is not extendable.
     */
    void set length(int newLength);
  
    /**
     * Adds [value] at the end of the list, extending the length by
     * one. Throws an [UnsupportedOperationException] if the list is not
     * extendable.
     */
    void add(E value);
  
    /**
     * Adds [value] at the end of the list, extending the length by
     * one. Throws an [UnsupportedOperationException] if the list is not
     * extendable.
     */
    void addLast(E value);
  