TSelf generic confusion [Answered]

public interface IFunctor<TSelf, T> where TSelf : IFunctor<TSelf, T>
{
    IFunctor<USelf, U> Map<USelf, U>(Func<T, U> f) where USelf : IFunctor<USelf, U>;
}

public readonly struct Maybe<T> : IFunctor<Maybe<T>, T>
{
    // ...

    IFunctor<USelf, U> IFunctor<Maybe<T>, T>.Map<USelf, U>(Func<T, U> f)
    {
        // Should actually apply the func, but just for demonstration rn
        return new Maybe<U>();
    }
}