Filter arguments - howto?

Creating my RESTful API and I'd like to use the filter arguments as described in the docs:
http://codeigniter.com/user_guide/incomi...ng-filters

However, the FilterInterface signatures for after() and before() doesn't allow me to access the arguments passed (even though they are passed from \CodeIgniter\Filters::run). As I cannot create my own implementations of after() and before() that includes the argument without breaking \CodeIgniter\Filters\FilterInterface I'm at a loss here.

Realizing that a patch for this would break all code implementing \CodeIgniter\Filters\FilterInterface I don't find that to be a good solution, but still I'm working on a patch.

Or, maybe I am missing something completely?