They did link an hour long conference talk (which I haven't watched), that I assume explains in more detail the kind of logging system that they're working with: https://www.youtube.com/watch?v=Dt0vx-7e_B0

I think that basically they want a class template magic_functor that can be invoked as below

    magic_functor<std::source_location::file_name()>::type

And then they could get a compile-time number corresponding to the file_name by doing:

    using T = magic_functor<std::source_location::file_name()>::type;
    int x = my_logging_lib_string_to_number<T>();

But unfortunately it simply doesn't work, because magic_functor is unwritable, because a `const char *` doesn't remember its size like a `const char[]` does.