Rails 3.1 Engine namespaces can creep into URLs in application layout

snippet.rb

# the following route generated in an application layout
link_to "Foo", :controller => "foo", :action => "bar" 

# when rendered from the action of an engine would
# try to generate the route
link_to "Foo", :controller => "myengine/foo", :action => "bar"

snippet2.rb

# routes.rb
match '/path' => 'foo#bar', :as => 'foo'

snippet3.rb

# if the current controller is "foo/bar/baz" and :controller => "baz/bat"
# is specified, the controller becomes "foo/baz/bat"
def use_relative_controller!
  if !named_route && different_controller?
    old_parts = current_controller.split('/')
    size = controller.count("/") + 1
    parts = old_parts[0...-size] << controller
    @controller = @options[:controller] = parts.join("/")
  end
end