class Regexp::Lexer

def break_codepoint_list(token)
  lead, _, tail = token.text.rpartition(' ')
  return if lead.empty?
  tokens.pop
  tokens << Regexp::Token.new(:escape, :codepoint_list, lead + '}',
            token.ts, (token.te - tail.length),
            nesting, set_nesting, conditional_nesting)
  tokens << Regexp::Token.new(:escape, :codepoint_list, '\u{' + tail,
            (token.ts + lead.length + 1), (token.te + 3),
            nesting, set_nesting, conditional_nesting)
  self.shift = shift + 3 # one space less, but extra \, u, {, and }
end