The attribute-use uniqueness check (ag-props-correct.2 / ct-props-correct.4)
flattens a complex type's or attribute group's uses through attributeGroup
references. A reference to a redefined group whose redefinition self-references its
former self stopped at the cycle guard, so the original's attributes were never
reached and a duplicate they cause was missed.
Expand a redefinition's self-reference to the group's pre-redefine base definition
(already retained in the context for this purpose) so the original's attributes
join the set; a genuine non-redefine cycle still terminates without contributing.
Separately, exclude use="prohibited" attributes from the duplicate-name and
single-ID counts: a prohibited use is a removal marker, not a member of
{attribute uses} (XSD 3.4.2 / 3.6.2). This is the spec-correct reading and keeps a
self-reference that re-imports an attribute and then prohibits it from being
counted as a duplicate.
This catches W3C XSTS attQ011 and attQ017. XSTS schema invalid-accepted 22 -> 20,
valid-rejected held at 0.
Mihaela Mihaljevic
41b3a707c3