class RuboCop::Cop::Naming::AsciiIdentifiers

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