anchor.diff:     * DOM element. The function's return value is then used to set each
      * element's attribute. A null value will remove the specified attribute.
      */
  -  attrFunc(final String name, final objectFunction fn) {
  +  void attrFunc(final String name, final objectFunction fn) {
       final qualified = core.qualify(name);
       if (qualified.space != null) {
         each((node, data, i, j) {
  
positive.code:    * Sets the attribute with the specified name to the specified value
     * on all selected elements.
     */
    attr(final String name, final Object value) {
      if (value == null) {
        attrNull(name);
        return;
  
negative.code:    * property set or removed as appropriate. When setting, the specified
     * priority is used.
     */
    void styleFunc(final String name, final objectFunction fn, [String priority=""]) {
      each((node, d, i, j) {
        final x = fn(node, d, i, j);
        if (x == null) {
  