# File lib/haml/filters.rb, line 327
      def template_class
        (@template_class if defined? @template_class) or begin
          @template_class = Tilt["t.#{tilt_extension}"] or
            raise Error.new(Error.message(:cant_run_filter, tilt_extension))
        rescue LoadError => e
          dep = e.message.split('--').last.strip
          raise Error.new(Error.message(:gem_install_filter_deps, tilt_extension, dep))
        end
      end