if you attempt to return a Voldemort type that defines value or index as a function, or stores it in a struct when you call for each you get an error like

auto front{
  struct dataaccess{
    int index;
    T value;
  }
  return dataacess(start,data[start]);
}

>Error: cannot infer argument types, expected 1 argument, not 2

It seems to require exactly an std.tuple, and the spec should say as much or clarify how it works