message: Don't declare new types for this
diff: @@ -22,14 +22,14 @@ namespace detail
  // Surface
  //
  -struct has_normals_tag : std::true_type {};
  -struct has_no_normals_tag : std::false_type {};
  +using has_normals_tag = std::true_type;
  +using has_no_normals_tag = std::false_type;
  -struct has_colors_tag : std::true_type {};
  -struct has_no_colors_tag : std::false_type {};
  +using has_colors_tag = std::true_type;
  +using has_no_colors_tag = std::false_type;
  -struct has_textures_tag : std::true_type {};
  -struct has_no_textures_tag : std::false_type {};
  +using has_textures_tag = std::true_type;
  +using has_no_textures_tag = std::false_type;
  template <typename T>
  struct has_normals_impl
  