message: Forward declaration of functions is necessary, friend declaration doesn't count.
diff: @@ -25,6 +25,9 @@ namespace asset
  class IGeometryCreator;
  class IMeshManipulator;
  + std::function<void(IAsset*)> makeAssetGreetFunc(const IAssetManager* const _mgr);
  + std::function<void(IAsset*)> makeAssetDisposeFunc(const IAssetManager* const _mgr);
  +
  class IAssetManager
  {
  // the point of those functions is that lambdas returned by them "inherits" friendship
  