FMaterialShader

Hi everyone!
I`am trying to make custom mobile shadows, did anyone try to implement FMaterialShader? I do all stuff like in source code (RemoteSessaionARCameraChannel.cpp) but seems like if i declare DECLARE_SHADER_TYPE(FMyShader, Material) and the try to implement like IMPLEMENTING_MATERIAL_SHADER_TYPE its not working(throw me error (not allowed external symbol _TypeLayoutDesc…), only if my shader is inherit from FShader its seems fine. But I guess that if I need VertexFactory in my vertex shader i need FMaterialShader, is it right? Or I do something wrong?