Default equality for generic formal types

["Matthew Heaney" <matthew_heaney@acm.org>]

Suppose I have a generic subprogram like this:

generic
  type Item_Type is private;
  with function Item_Eq (L, R : Item_Type)
    return Boolean is "=";
procedure Generic_Op (O : T);


Suppose further that the generic actual type is nontagged, and has
overridden its predefined equality.

To which equality does Item_Eq refer?  The overridden version, or the
predefined version?  What does that default value for Item_Eq, "=", mean
at the time of compilation of the generic?

If the client does not explicitly pass in an item equality op during the
instantiation (likely, because the type is nonlimited), then inside
Generic_Op, what does Item_Eq refer to?  Predefined equality, or the
overridding version?

Thanks in advance,
Matt