lib/active_support/core_ext/kernel/concern.rb



require 'active_support/core_ext/module/concerning'

module Kernel
  module_function

  # A shortcut to define a toplevel concern, not within a module.
  #
  # See Module::Concerning for more.
  def concern(topic, &module_definition)
    Object.concern topic, &module_definition
  end
end