I don’t think the code being compiled in my_lib can see the code in my_app at all - it would massively complicate dependency tracking if files in the application could cause libraries to recompile.
Have you considered an approach like Ecto.Repo where callers say use MyLib, modules: [...etc...] in a module in my_app? The for loop and friends stay in my_lib but the use of them happens when my_app is compiled.
