class RuboCop::Cop::Style::AsciiComments

def first_non_ascii_chars(string)
  string.match(/[^[:ascii:]]+/).to_s
end

def first_offense_range(comment)
  expression    = comment.loc.expression
  first_offense = first_non_ascii_chars(comment.text)
  start_position = expression.begin_pos +
                   comment.text.index(first_offense)
  end_position   = start_position + first_offense.length
  range_between(start_position, end_position)
end

def investigate(processed_source)
  processed_source.comments.each do |comment|
    unless comment.text.ascii_only?
      add_offense(comment, first_offense_range(comment))
    end
  end
end