class Regexp::Syntax::Base

def normalize_backref(type, token)
  case token
  when :name_ref_ab, :name_ref_sq
    [:backref, :name_ref]
  when :name_call_ab, :name_call_sq
    [:backref, :name_call]
  when :name_nest_ref_ab, :name_nest_ref_sq
    [:backref, :name_nest_ref]
  when :number_ref_ab, :number_ref_sq
    [:backref, :number_ref]
  when :number_call_ab, :number_call_sq
    [:backref, :number_call]
  when :number_rel_ref_ab, :number_rel_ref_sq
    [:backref, :number_rel_ref]
  when :number_rel_call_ab, :number_rel_call_sq
    [:backref, :number_rel_call]
  when :number_nest_ref_ab, :number_nest_ref_sq
    [:backref, :number_nest_ref]
  else
    [type, token]
  end
end