module Regexp::Expression::Shared::ClassMethods

def construct(params = {})
  attrs = construct_defaults.merge(params)
  options = attrs.delete(:options)
  token_args = Regexp::TOKEN_KEYS.map { |k| attrs.delete(k) }
  token = Regexp::Token.new(*token_args)
  raise ArgumentError, "unsupported attribute(s): #{attrs}" if attrs.any?
  new(token, options)
end

def construct_defaults
  if self == Root
    { type: :expression, token: :root, ts: 0 }
  elsif self < Sequence
    { type: :expression, token: :sequence }
  else
    { type: token_class::Type }
  end.merge(level: 0, set_level: 0, conditional_level: 0, text: '')
end

def token_class
  if self == Root || self < Sequence
    nil # no token class because these objects are Parser-generated
  # TODO: synch exp class, token class & type names for this in v3.0.0
  elsif self == CharacterType::Any
    Regexp::Syntax::Token::Meta
  else
    Regexp::Syntax::Token.const_get(name.split('::')[2])
  end
end