class RuboCop::Cop::Style::WhileUntilModifier

def on_while(node)
  return unless node.multiline? && single_line_as_modifier?(node)
  add_offense(node.loc.keyword, message: format(MSG, keyword: node.keyword)) do |corrector|
    oneline = "#{node.body.source} #{node.keyword} #{node.condition.source}"
    corrector.replace(node, oneline)
  end
end