class RuboCop::Cop::Rake::DuplicateNamespace

def on_namespace(node)
  namespaces = namespaces(node)
  return if namespaces.include?(nil)
  full_name = namespaces.reverse.join(':')
  if (previous = @namespaces[full_name])
    message = message_for_dup(previous: previous, current: node, namespace: full_name)
    add_offense(node, message: message)
  else
    @namespaces[full_name] = node
  end
end