feat(kernel): R7b Swift walker — swift module, tree-sitter-swift 0.7.3 bump, swift default-routed (#1381)

Fifth R7b batch-3 port, checklist-first recipe
(docs/design/swift-kernel-port-checklist.md, 1,056 lines — the largest of the
arc, with a built-extractor-validated emission pin and a childForFieldName
truth table).

Grammar bump first, validated standalone: tree-sitter-wasms ^0.4.0 (ABI 13) →
crate 0.7.3 — with a provenance twist: the wasm is built from the CRATE
TARBALL's src/ (alex-pinkus keeps generated files off main and the
0.7.3-with-generated-files tag ships an older ABI-14 generation that can never
sha-match; grammar.json rules are JSON-equal; the tarball is byte-for-byte
what the kernel's cargo build compiles — table identity by construction).
Older crates evaluated and rejected: clean-parse shapes are byte-identical on
0.7.3 (53-line CST battery diff, all inert), so an older pin buys nothing and
loses the macro-era wins. Delta = error-set membership (63 old-error files
parse clean: swift-testing #expect, #Preview/#GET macros, package access,
typed throws — vapor 23.1%→9.3%; 21 NEW-only regressions in 3 probed
construct classes) + two gate-found categories: docstring boundaries near #if
directives (7 clean files, docstring-field-only — verified mechanically) and
array-literal-callee call refs (2 refs, 1 file). Every hunk classified via
the error-union rule + parked-ref↔edge ripple pairing.

Walker (the arc's biggest) centers on the #1020 DEDICATED property branch:
computed properties → property nodes with the getter walked under the
property (SwiftUI body), static let/var → constant/variable, stored → field,
decorator/type-annotation/@Siblings-attr-arg refs all attached to the
ENCLOSING TYPE, stored initializer calls attributed to the class. Preserved
bug-for-bug: the never-resolving 'parameter' field (zero param type refs,
zero signatures), present-false isAsync, open→internal visibility,
everything-is-extends inheritance (first type_identifier per specifier), no
instantiates refs ever, subscript reads as `calls arr`, `defer` as `calls
defer`, multi-case enum entries minting only the first case, /** */ block
docs ignored AND chain-breaking, init/deinit/subscript minting no nodes with
visitNode-routed bodies (calls → class, static reads → nothing), multi-
segment extension resolveName, sugar extension names, the #selector shapes,
and the value_argument label-forward skip. ONE fix found by the sweep (then
pinned in the fixture + checklist): the shared `assignment` shadow-prune case
is swift-live — declared-then-assigned `let X: T` prunes X as a value-ref
target.

Gates: sweeps 0-diff Alamofire 89/98, vapor 224/247, swift-nio 407/554
(--max-deferral 0.3 — swift error incidence is 9–27% on BOTH arms,
structural; every deferral count matches the survey's table exactly);
full-init dumps byte-identical ×3 (31.9k/20.7k/126.3k lines); the Alamofire
census reproduces property=348 (the #1020 number) on the kernel arm;
kernel-swift-parity suite (206-line torture + CRLF + the #if-between-enum-
cases defer fixture) + swift grammar-parity row; full suite 2,626 green ×2
under CODEGRAPH_KERNEL_EXPECT=1. DEFAULT_ROUTED += swift (14 langs).

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/extraction/grammars.ts

@@ -313,6 +313,15 @@ const VENDORED_WASM_LANGS: ReadonlySet<GrammarLanguage> = new Set([
   // tarball. Replaces the ^0.22 tree-sitter-wasms build (ABI 14 → 15). NOT
   // graph-neutral — the classified delta list lives in the php checklist doc.
   'php',
+  // R7b (Swift kernel port prep): tree-sitter-swift crate 0.7.3. Built from
+  // the CRATE TARBALL's src/ (NOT a tag sha-match: alex-pinkus keeps
+  // generated files off main and the 0.7.3-with-generated-files tag ships an
+  // older ABI-14 generation; grammar.json rules are JSON-equal, and the crate
+  // tarball is byte-for-byte what the kernel's cargo build compiles — table
+  // identity by construction). Replaces the ^0.4.0 tree-sitter-wasms build
+  // (ABI 13 → 15). NOT graph-neutral — delta is error-set membership only;
+  // classified list in the swift checklist doc.
+  'swift',
 ]);
 
 /** Absolute path of a language's grammar WASM (vendored or tree-sitter-wasms). */

src/extraction/kernel/index.ts

@@ -68,6 +68,12 @@ const DEFAULT_ROUTED: ReadonlySet<Language> = new Set<Language>([
   // symfony (13,950 files byte-parity) + full-init dump-diffs byte-identical
   // ×3. Deferral ≈0–0.1% (genuinely-broken fixtures) — default sweep guard.
   'php',
+  // R7b (2026-07-20): parity swept 0-diff on Alamofire/vapor/swift-nio (720
+  // clean files byte-parity; Alamofire's 348 #1020 property nodes reproduced
+  // exactly) + full-init dump-diffs byte-identical ×3. Swift error incidence
+  // is structurally 9–27% on BOTH arms (heavy #if conditionalization) —
+  // sweeps run --max-deferral 0.3; a deferral-rate JUMP is the bug signal.
+  'swift',
 ]);
 
 /**