A redefinition of an attributeGroup that self-references the original re-imports
all of its attribute uses, so directly re-declaring one of those attributes
produces two attribute uses of the same name, a duplicate forbidden by
ag-props-correct.2.
Flag a non-prohibited direct re-declaration of an attribute the original directly
declares, when the redefinition has a self-reference. To stay false-positive-free
the check fires only when both the original and the re-declaration land in no
namespace (a qualified attribute's target namespace depends on cross-document
form/chameleon resolution, so it is not compared); a self-referencing redefinition
that adds genuinely new attributes (attgC007/attgC038/groupB018) stays valid.
Also extracts the use-transition restriction errors into a helper to keep the
function within the complexity limit.
This catches W3C XSTS schM8. XSTS schema invalid-accepted 23 -> 22, valid-rejected
held at 0.
Mihaela Mihaljevic
64e30fe491