menu_tree_output defining theme suggestions with impossible function names

This is a code snippet from menu_tree_output():

$element['#theme'] = 'menu_link__' . $data['link']['menu_name'];

As you can see, the function here defines a theme suggestion that uses the base theme function theme_menu_link() but also the menu's name as additional possibility for menu specific theming. The problem is, that menus often have a "-" in their name like for example main-menu or secondary-links. For those it is impossible to invoke a function since "-" is not allowed in function names. The menu_tree_output() function should check the menu name string for forbidden signs before and strip it accordingly.