class RuboCop::Cop::Rails::NotNullColumn

def check_change_table(node)
  change_table?(node) do |table|
    next unless node.body
    children = node.body.begin_type? ? node.body.children : [node.body]
    children.each do |child|
      check_add_column_in_change_table(child, table)
      check_add_column_via_shortcut_in_change_table(child, table)
      check_add_reference_in_change_table(child, table)
    end
  end
end