chain.rb

module TrackAddedMethods  
  def method_added(meth)
    @__added_methods ||= []
    @__added_methods << meth
  end
  
  def __added_methods
    @__added_methods
  end
end

class Module
  inline do |builder|
    builder.include "\"node.h\""
    builder.c <<-C
      VALUE copy_method(VALUE klass, VALUE symbol) {
        ID id = rb_to_id(symbol);
        NODE *node = NULL;
        st_table *other_method_table = RCLASS(klass)->m_tbl;
        st_table *method_table = RCLASS(self)->m_tbl;
        if(st_lookup(other_method_table, id, (void *)&node)) {
          st_insert(method_table, (st_data_t)id, (st_data_t)node);
          return Qtrue;
        } else {
          rb_raise(rb_eRuntimeError, "No such method `%s' on %s", rb_id2name(id), STR2CSTR(rb_mod_name(klass)));
        }
      }
    C
  end

  def __move_to_module(*meth_names)
    me = self
    mod = Module.new do
      meth_names.each do |name|
        copy_method me, name
      end
    end
    meth_names.each do |name|
      remove_method name
    end
    include mod
  end
  
  def override(&blk)
    mod = Module.new do
      extend TrackAddedMethods
    end
    mod.class_eval(&blk)
    __move_to_module(*mod.__added_methods)
    include mod
  end
end