Group @testable imports at the bottom, per public/rules-swift's swiftformat. A
behavior-preserving import-ordering reformat across 252 files (mostly tests).
--trailingclosures was deliberately not adopted (cosmetic, and swiftformat flags
it as caution-worthy).
The instance-validity derivation and substitution tables were keyed by bare
local name, so two same-local-name types or elements in different namespaces
collided. In multi-document validation this let one schema's block/derivation
facts shadow another's, and it blocked honouring blockDefault (whose re-land
widened that collision into an over-rejection).
Key the instance subsystem by namespaced identity {ns}local instead. The shared
DerivationTables keeps its bare-keyed fields for the schema-validity machinery
(Particle-Valid-Restriction and the consistency rules, which resolve QNames to
bare names and walk the same backbone) and gains parallel ns* fields built in
the same pass, resolving each container's components through its target
namespace and prefix bindings. Only the instance consumers
(blockedSubstitutionError, notDerivedSubstitutionError, abstractTypeError, the
substitution-group closure, and referenceParticle) read the ns* tables, via a
derivationKey(fromReference:) that reduces a type:{ns}local reference, a bare
name, or an element ref to a {ns}local backbone key. A key miss stays permissive
(no constraint, substitution allowed), so the re-keying cannot over-reject.
With the namespaced backbone in place, blockDefault is re-landed FP-free: a
schema's blockDefault supplies the {disallowed substitutions} of every element
and complex type without an explicit block (own block overrides; block="" clears;
intersected with the methods each component admits), so blockDefault="extension"
bars an extension substitution and "#all" bars all, without one namespace's
defaults shadowing another's.
The pure re-keying preserves single-document behaviour exactly (the corpus is
overwhelmingly single-namespace, where {ns}local and bare coincide): all four
XSTS buckets held at vsr=0 / isa=69 / vir=0 / ivi=89 after re-keying alone.
blockDefault then drove invalid-instances-accepted 89 to 81, no false positive
(valid-instances-rejected and valid-schemas-rejected held at 0), no other bucket
moved. An adversarial review exercised same- and cross-namespace substitutions,
no-targetNamespace keys, simple-type restriction, transitive substitution groups,
and blockDefault override/over-block cases, and the prior multi-document
cross-namespace blockDefault over-rejection is now accepted while a same-namespace
blocked substitution is still rejected (precise, not merely permissive).
