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).
A model group may not contain itself (mg-props-correct.2), an attribute group
may not reference itself transitively (ag-props-correct.3), and a substitution
chain may not loop (e-props-correct.6).
The model-group check follows references only within a definition's own
compositor tree, stopping at element and type boundaries: a group referenced
inside an element's content is a recursive data structure (permitted), not the
group containing itself (particlesZ010, addB077). A reference is followed only
when it resolves to the schema's own target namespace; a group or attribute
group redefined in xs:redefine ends the chain (its single self-reference is the
legal redefinition).
XSTS: invalid schemas accepted 516 to 505 (attgC010/020/031, attgD015,
groupB012-015, addB180, xsd009.e, xsd010.e now rejected), no other bucket
raised. A genuine cycle introduced across two redefined definitions is a
disclosed under-rejection (an adversarial critic's only finding).
A complex or simple type may not derive, transitively through its base, from
itself. Such schemas were accepted. The check walks the base chain built from
each type's complexContent/simpleContent extension/restriction base (and a
simpleType's restriction base), following an edge only when the base resolves to
the schema's own target namespace.
Three exceptions keep it from over-rejecting: element content that recurses (an
element of the type's own type) is not a derivation and is not followed; a type
redefined in xs:redefine legitimately names itself as its base, so redefined
types end the chain; and the ur-types (anyType/anySimpleType/anyAtomicType,
which the schema-for-schemas bootstraps with self-referential definitions) end
the chain. The target-namespace gate prevents a local type whose base is a
same-local-name type in another namespace from being mistaken for a self-cycle
(found by an adversarial critic; the engine resolves by local name).
XSTS: invalid schemas accepted 519 to 516 (addB101, elemM003, xsd007.e now
rejected), no other bucket raised. Union/list and genuine cross-namespace
derivation cycles are a disclosed under-rejection.
