class RuboCop::Cop::Style::TrailingUnderscoreVariable

def autocorrect(node)
  left, right = *node
  variables = *left
  first_offense = find_first_offense(variables)
  end_position =
    if first_offense.loc.expression == variables.first.loc.expression
      right.loc.expression.begin_pos
    else
      node.loc.operator.begin_pos
    end
  range =
    Parser::Source::Range.new(node.loc.expression.source_buffer,
                              first_offense.loc.expression.begin_pos,
                              end_position)
  ->(corrector) { corrector.remove(range) unless range.nil? }
end

def find_first_offense(variables)
  first_offense = nil
  variables.reverse_each do |variable|
    break unless variable.children.first == :_
    first_offense = variable
  end
  first_offense
end

def on_masgn(node)
  left, = *node
  variables = *left
  first_offense = find_first_offense(variables)
  return if first_offense.nil?
  range =
    Parser::Source::Range.new(node.loc.expression.source_buffer,
                              first_offense.loc.expression.begin_pos,
                              variables.last.loc.expression.end_pos)
  add_offense(node, range)
end