WordPress menu walker classes for custom post types and archives.

functions.php

<?php

/**
 * Walker
 * 
 * @see http://codex.wordpress.org/Class_Reference/Walker
 * @see https://github.com/WordPress/WordPress/blob/3.9.1/wp-includes/nav-menu-template.php#L351-L358
 */
function prefix_nav_menu_objects( $sorted_menu_items ) {
	$walker = new Pronamic_WP_Walker_Nav_Menu_Classes();

	$walker->walk( $sorted_menu_items, 0 );

	return $sorted_menu_items;
}

add_filter( 'wp_nav_menu_objects', 'prefix_nav_menu_objects' );

/**
 * Walker
 */
class Pronamic_WP_Walker_Nav_Menu_Classes extends Walker_Nav_Menu {
	private $archive_url;

	private $elements;

	public function __construct() {
		$this->elements = array();

		$post_type = get_query_var( 'post_type' );

		$this->is_singular = is_singular();
		$this->is_archive  = is_post_type_archive();

		$this->archive_url = get_post_type_archive_link( $post_type );
	}

	function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
		if ( $this->archive_url == $item->url ) {
			if ( $this->is_archive ) {
				$item->classes[] = 'prefix-current-archive';
			}

			if ( $this->is_singular ) {
				$item->classes[] = 'prefix-current-archive-ancestor';	
			}

			$this->active[ $depth ] = true;
		}
	}

	function end_el( &$output, $item, $depth = 0, $args = array() ) {
		$depth_child = $depth + 1;

		if ( isset( $this->active[ $depth_child ] ) ) {
			$item->classes[] = 'prefix-current-custom-ancestor';

 			$this->active[ $depth ] = true;

			unset( $this->active[ $depth_child ] );
		}
	}
}