# File lib/sass/script/functions.rb, line 335
      def assert_type(value, type, name = nil)
        return if value.is_a?(Sass::Script.const_get(type))
        err = "#{value.inspect} is not a #{type.to_s.downcase}"
        err = "$#{name}: " + err if name
        raise ArgumentError.new(err)
      end