The substitution-group filter drops a member when the head element's
{disallowed substitutions} (or the head type's {prohibited substitutions}) blocks
the method by which the member's type derives from the head's type. It looked the
member's type up in the named derivation backbone, so a member with an INLINE
(anonymous) complex type had no entry and was never dropped, even when its inline
type extended the head's type and the head blocked extension.
Record an inline-typed element's derivation under a synthetic key (the element key
plus a `#` marker no QName can contain, so it cannot collide with a real type and
is unreachable as any other type's derivation base) so the filter can see the
member's method. A member reaching the head's type by an unblocked method, a plain
inline type with no derivation, and same-local-name elements in different
namespaces are all unaffected.
This catches W3C XSTS disallowedSubst00105m (and a sibling). XSTS
invalid-instances-accepted 25 -> 23, valid-instances-rejected held at 0.
Mihaela Mihaljevic
18fd42b726