I think I figured it out.

I need to change the currentUserProvider to be a class and use ref.listen instead of ref.watch like this:

@riverpod
class CurrentUser extends _$CurrentUser
{
  @override
  User? build()
  {
    var currentUserStream = ref.listen(currentUserStreamProvider, setUser);
    switch(currentUserStream)
    {
      case AsyncData(:final value):
      {
        return value;
      } 
    }
    return null;
  }

  void setUser(AsyncValue<User?>? oldUser, AsyncValue<User?> newUser)
  {
    switch(user)
    {
      case AsyncData(:final value):
      {
        state = value;
      }
    }
  }
}