Descriptions of the method lookup algorithm normally describe a path
from the very eigenclass of an object up to the resolution of
method_missing. For example check Flanagan & Matz, pages 258--259.

Until now I visualized entities having pointers to classes and
modules, who had tables of method names. So my idea was that, for
example, resolving a method invoked on some object may eventually
follow the pointer to its class, and look at its method table as
defined at that moment. If the method is founded there it is executed.
Fine.

But I just realized there's undef_method, that prevents looking up the
hierarchy:

    class C
      def croak; end
    end

    class D < C
      undef_method :croak
    end

    C.new.corak # fine
    D.new.croak # NoMethodError

Hence, I guess the method lookup algorithm does a bit more of work,
there's going to be a black list to check or something like that where
undef_method moves stuff.

Anyone?