concern3.rb

module ActiveSupport
  module Concern
    def append_features(base)
      if base.instance_variable_defined?(:@_dependencies) 
        base.instance_variable_get(:@_dependencies) << self
      return false
      else
      return false if base < self
        @_dependencies.each { |dep| base.send(:include, dep) }
      super
      base.extend const_get(:ClassMethods) \
      if const_defined?(:ClassMethods)
    # ...
  end
end
# ...