class YARD::Parser::Ruby::ParameterNode

def args_forward
  # shape is (required, optional, rest, more, keyword, keyword_rest, block)
  # Ruby 3.1 moves :args_forward from rest to keyword_rest
  args_index = YARD.ruby31? ? -2 : 2
  self[args_index].type == :args_forward if self[args_index]
end

def block_param
  self[-1] ? self[-1][0] : nil
end

def double_splat_param
  return nil unless YARD.ruby2?
  if (node = self[-2]).is_a?(AstNode)
    if node.type == :ident
      node
    elsif node.type == :kwrest_param
      # See https://bugs.ruby-lang.org/issues/12387
      node.last
    end
  end
end

def named_params
  return @named_params if defined?(@named_params)
  if YARD.ruby2? && self[-3] && self[-3][0] && self[-3][0].type == :named_arg
    @named_params = self[-3]
  else
    @named_params = nil
  end
end

def splat_param
  self[2] ? self[2][0] : nil
end

def unnamed_end_params
  self[3]
end

def unnamed_optional_params
  return @unnamed_optional_params if defined?(@unnamed_optional_params)
  params = self[1] || []
  if self[-3] && self[-3][0] && self[-3][0].type == :unnamed_optional_arg
    params += self[-3]
  end
  @unnamed_optional_params = params.empty? ? nil : params
end

def unnamed_required_params
  self[0]
end