Finding out what formats an action can respond to

In a layout, I'd like to write something like

  <% if has_format?(:foo) -%>
    <%= link_to 'Foo version', :format => :foo %>
  <% end %>

Grabbing into protected method territory, I can even define a suitable
helper method

  def has_format?(format)
    controller.send(:collect_mimes_from_class_level).include?(format)
  end

(see action_controller/metal/mime_responds.rb)

I'd much rather have an official method, say
ActionController::MimeResponds#responds_to?(format), and a helper method
#has_format?(format) defined in terms of it. As the name #responds_to?
is dangerously close to #respond_to?, #responds_to_format? may be safer,
if less pretty. Also, it might be a good idea for
#collect_mimes_from_class_level to memoize its result.

Is there any reason against this? A better way?

Michael