codegraph/docs/design/scala-kernel-port-checklist.md

Scala kernel port (R7b) — the bug-for-bug checklist

Status: SURVEY COMPLETE (2026-07-20), port not started. Survey basis: every TS-side branch a .scala/.sc file exercises, with file:line anchors as of 45a53eb (HEAD at survey time, clean main; a6c62d7..45a53eb touched only grammars.ts/kernel/index.ts/wasm inside src/extraction — tree-sitter.ts, languages/scala.ts, function-ref.ts, and tree-sitter-helpers.ts are byte-unchanged, so kotlin/swift-checklist anchors into shared code remain valid). Every grammar-shape claim below was probed against the production vendored wasm (dist/extraction/wasm/tree-sitter-scala.wasm, sha256 7945b13e…, identical to src/…), and every extraction-behavior claim was pinned against the real dist/ extractor (extract-*.txt ground-truth dumps) — not derived from code reading. childForFieldName truth tables were probed directly (brace-field.out, the FIELDS sections of cst-snippets.txt) because this grammar attaches field names to ANONYMOUS tokens — CST dump labels alone mislead (the swift lesson, §Extension). Probe scripts + dumps in the session scratchpad svy-scala/ (§Probe artifacts). Read WITH docs/design/rust-kernel-migration-plan.md (§0a recipe, §2 boundary, §4 tracker row "scala", §5 gates) and the format precedents (kotlin-kernel-port-checklist.md — the closest sibling: JVM family, hook property branch, re-encode gate — and swift-kernel-port-checklist.md).

Blocking findings: none — but three eyes-open items. (1) The wasm is already vendored and needs NO bump: VENDORED_WASM_LANGS has contained scala since 2026-05-07 (#91), and the vendored wasm is table-identical to tree-sitter/tree-sitter-scala master@0aca5d0a6f (verified twice: the batch-4 positional table compare, and this survey's clone-sha match). The port is vendored-grammar-C only (kotlin mechanism) — there is no behavior-delta gate to run. (2) Error incidence is bimodal: mainstream Scala-2-style repos are clean (os-lib 0.00%, cats 1.80%) but bleeding-edge Scala-3 code is not (scala3 compiler/src 9.88%, library/src 17.79% — capture-checking ^ types), and ~40–60% of erroring files are PHANTOMS (hasError=true, zero ERROR/missing nodes — trust the flag). Sweep guidance in §Architecture #6. (3) scala has 32 real fields but three load-bearing places where childForFieldName returns the FIRST of SEVERAL same-named fields — or an anonymous { token (import path, curried parameters, extension body). The walker must reproduce first-match-wins over the full (named+anonymous) child list, not "the" field (§Extractor config, §Extension).

Grammar prep (NO wasm bump — vendored-C kernel build only)

• Production wasm: src/extraction/wasm/tree-sitter-scala.wasm, sha256 7945b13e6f9b15b578c5e5e4e60253c049fec07c531518163f3415a76c0621aa (src == dist byte-identical), ABI 15, STATE_COUNT 26650, 357+5 symbols, FIELD_COUNT 32. In VENDORED_WASM_LANGS (grammars.ts:292) since #91 (2026-05-07). Mapping scala: 'tree-sitter-scala.wasm' (grammars.ts:38).
• Provenance (verified): tree-sitter/tree-sitter-scala master@0aca5d0a6fe115b16d55cb100e1bb05e7fb11385 (2026-04-22 "chore: generate and sync from ec71cd9d51" — the post-v0.26.0 fix batch: scala2-compiler-100%, lambda-body restrict, wildcard self-type). The clone's src/parser.c sha256 equals the batch-4 probe's positional-table-verified copy (bc3c3c79…), and that probe found the wasm's kind/field tables positionally identical to it. The v0.26.0 tag == crate 0.26.0 is 26620 states — 30 states BEHIND our wasm — so a crate pin would be a silent downgrade; later master (fc99b1bd, Apr-27) is a 23959-state restructure — a future-bump candidate, NOT this port. Full record: ../scratchpad/batch4-grammar-probe.md.
• Vendored-C route (kotlin mechanism, second use) — copy from the 0aca5d0a6f clone into codegraph-kernel/grammars/scala/ (shas recorded in a comment; survey record grammar-shas.txt):
  • src/parser.c bc3c3c794f19461d99d04de6c31d57fa3e41243509b9ab023a9b88ed3273d102 (34,970,232 bytes — 35 MB, the biggest grammar in the tree; expect a slow cc step)
  • src/scanner.c e4ba242568ee3493015598997bf60f613802616eade62717c21109287ef64752 (17,731 bytes — a REAL external scanner: significant-indentation + interpolation; it handles \r explicitly, scanner.c:476)
  • src/tree_sitter/alloc.h b29c1c9f…, array.h 31e60a1b…, parser.h 180b893c…
  • build.rs: crib the upstream bindings/rust/build.rs flag set — cc::Build .std("c11").include(grammars/scala).flag_if_supported("-Wno-unused"), msvc -utf-8; compile parser.c + scanner.c; symbol tree_sitter_scala (parser.c:1199034). Same shape as the kotlin block (build.rs:14-22).
  • Cargo: tree-sitter-language shim already present (kotlin). langs.rs: extern "C" { fn tree_sitter_scala() -> *const (); } + "scala" => LanguageFn::from_raw(...) + LANGUAGES 15 → 16.
  • __tests__/kernel-grammar-parity.test.ts:39 GRAMMAR_LANGUAGES += 'scala' — the id-by-id table compare against the vendored wasm proves the C build is the same revision (ABI 15 / 26650 states / 32 fields must match).
  • License: MIT (tree-sitter org). No metadata shim needed (repo has tree-sitter.json-era layout; we never run tree-sitter generate).
• NO grammar-bump gate. Unlike every other R7b language there is no old-vs-new wasm diff to run — production already parses with this exact revision. The kernel-grammar-parity row IS the alignment proof.
• Scanner-state parity risks — probed clean: the indentation scanner handles CRLF: LF-vs-CRLF parses are s-expression-identical on every fixture including Scala-3 indentation syntax (crlf-cst.cjs: indent/ torture/docs/vref/misc/ext/script all sexpEqual=true, no error flips). Extraction under CRLF is byte-identical except the multi-line-block-comment docstring \r retention (§Docstrings — a shared js_multiline_strip concern, not a scanner one). The kernel parses UTF-8 while wasm parses UTF-16 — error-recovery differences are exactly what per-file has_error() → defer: guards; nothing scala-specific beyond the elevated incidence below.

Error incidence (production wasm, all .scala/.sc ≤1 MiB, error-sweep.cjs)

Repo	files	hasError	rate	of which PHANTOM
os-lib (small)	59	0	0.00%	—
cats (medium)	835	15	1.80%	4 (27%)
scala3 compiler/src	577	57	9.88%	—
scala3 library/src	652	116	17.79%	69 (59%)
scala3 whole repo	18,411	1,991	10.81%	(incl. tests/ = deliberately-invalid neg fixtures, 11.78%)

.sc files: 14 in scala3 (1 error); os-lib/cats have none. Error classes (sampled err-samples.out, minimized errvariants.out / phantom-min.out):

• (a) PHANTOM hasError — the dominant scala-3 class. hasError=true with a COMPLETE, correct CST and ZERO ERROR/missing nodes. Minimal repro: capture-checking postfix ^ — def f(x: List[Int]^): Int = 1 (the whole scala3 library uses import language.experimental.captureChecking). cats' scala-2 macro files (FreeFoldStep.scala) phantom too. The kernel must defer on the FLAG, never on ERROR-node presence (kotlin lesson, worse here).
• (b) end used as an identifier — end is hard-reserved by the grammar (end match, val end = 1 both ERROR). cats AndThen.scala.
• (c) generic + curried super-constructor args — extends Eq[A]()(ev) ERRORS (plain Base(1)(2) parses clean — extract-super2.txt). cats kernel instances.
• (d) Unicode symbolic type names — type ⊥ = Nothing (cats package.scala).
• (e) scala 3.0–3.3 given … with { } syntax — given x: C with { … } ERRORS (the = new C {} and colon forms parse fine).
• (f) assorted dotty-frontier syntax (union-of-singleton .type unions, compact catch case, braceless match at margin) — scala3 compiler files.

All classes are grammar-inherent and identical across arms by construction (same grammar revision compiled twice). Deferral guidance: §Architecture #6.

Architecture decisions

1. No preParse, no POST_PASSES. scalaExtractor has no preParse (languages/scala.ts — whole file) → the kernel/index.ts preParse hoist is a no-op; no POST_PASSES entry → tryKernelExtractRaw stays eligible.
2. One framework resolver can force the DECODED path for scala: playResolver (resolution/frameworks/play.ts:30, languages: ['scala', 'java', 'yaml'], and it HAS extract()), via parse-worker.ts's frameworksNeedDecode check (parse-worker.ts:95-100). detect() (play.ts:32): build.sbt matching /playframework|"play"|sbt-plugin|PlayScala|PlayJava/i, OR conf/routes exists, OR conf/application.conf exists. None of the three gate repos trips it (no conf/, no playframework in build.sbt) — they exercise the raw buffers-to-store transport; a Play app (or any repo with a root conf/application.conf — akka-style apps can!) is the decoded-path smoke check. The Play extract() itself only produces output for conf/routes/*.routes files (isPlayRoutesFile, grammars.ts:222-228) which are NOT scala files (extensionless → no-grammar path) — the cost of detection is only the decode, not wrong output.
3. One walker module (codegraph-kernel/src/scala.rs), registered in langs.rs; per-file has_error() → defer:. kotlin.rs is the closest crib (visitNode-hook property branch, classify-by-node-type, re-encode gate, JVM import shapes) but scala diverges in TEN places, each detailed below: (a) no namespace node ever (no packageTypes — package headers are ignored; QNs are bare); (b) functionTypes EMPTY → every def routes through the methodTypes branch (extractMethod → top-level fallback to extractFunction); (c) the val/var hook keys on the enclosing-definition NODE TYPE walk, not the stack; (d) getSignature is LIVE (fields exist) with the curried/type-params first-field quirk; (e) extension/given/ package_object have NO ladder branch — their leak-through behaviors are the port's hardest part; (f) instance_expression ∈ INSTANTIATION_KINDS + scalaBaseTypeName; (g) the scala extends branch iterates ALL supertypes; (h) scala-only type-annotation walks (every parameters + type_parameters context bounds) plus the hook's own emitScalaTypeRefs; (i) fn-ref spec with bare-identifier idTypes + postfix eta unwrap; (j) imports named by the FIRST path segment. No c/cpp-style dialect, no content sniffing: .scala and .sc both → scala (grammars.ts:120-121; .sbt is NOT mapped — build.sbt files are never indexed).
4. .sc files are ordinary scala files whose top-level statements attribute calls to the FILE node (pinned extract-script.txt: calls println/runTop from=file, top-level val → constant with file parent). Same for .scala files with top-level statements (grammar accepts them).
5. REF_FLAG_FILE_PATH (wire v2 slot) is NOT needed. No scala path emits refs carrying filePath (hook refs via emitScalaTypeRefs carry fromNodeId/name/kind/line/column only; extractImport sets no handledRefs; verified across every ground-truth dump — zero refs printed a filePath). Node decorators are likewise never set (no extractModifiers hook) — the decorator channel is decorates REFS only.
6. Deferral expectations: os-lib 0, cats 15/835 = 1.8%, but Scala-3-heavy repos run 10–18% (§Grammar prep table) with phantom-dominated error sets. Default --max-deferral 0.1 HOLDS on os-lib/cats and on mainstream Scala-2 style; sweeps over scala3-style repos need --max-deferral 0.3 (swift precedent). A deferral-rate JUMP on cats/os-lib is the bug signal; a big number on dotty-frontier code is grammar reality.

Extractor config (languages/scala.ts — 212 lines, read it whole)

Types: functionTypes=[] (comment: "top-level function_definition is handled via methodTypes"); classTypes=[class_definition, object_definition, trait_definition]; methodTypes=[function_definition, function_declaration]; interfaceTypes=[]; structTypes=[]; enumTypes=[enum_definition]; enumMemberTypes=[] (hook-handled); typeAliasTypes=[type_definition]; importTypes=[import_declaration]; callTypes=[call_expression]; variableTypes=[] and fieldTypes=[] (hook); extraClassNodeTypes=[]. nameField=name, bodyField=body, paramsField=parameters, returnField=return_type. interfaceKind=trait (unused in practice — extractInterface is unreachable, see §dispatch).

Field semantics (32 real fields — but first-match-wins bites 3×): childForFieldName(f) returns the FIRST child carrying field f, and in this grammar (i) several parents attach the same field to MULTIPLE children, and (ii) anonymous tokens can carry fields (probed, brace-field.out): braced extension (t: Int) { … } puts field body on {, the function_definition, and } — first match is the { token with namedChildCount 0; a for header puts enumerators on {/enumerators/}. The walker's field lookup must scan the FULL child list (named + anonymous) in order, exactly like tree-sitter's ts_node_child_by_field_name.

Hooks PRESENT (port each exactly):

• visitNode (scala.ts:131-198) — runs for EVERY node the main walker visits (tree-sitter.ts:943-953; NOT in visitFunctionBody). Three branches:

  1. val_definition / var_definition (:135-170) — the LIVE branch. Name via getValVarName (:5-11): pattern field; identifier → its text; else the pattern's first DIRECT namedChild of type identifier (val (ta, tb) → ONE node named ta spanning the whole val; val Some(v) → v; val multiA, multiB = 5 → multiA only — pinned, unlike kotlin's mint-nothing destructuring); no identifier → return false (falls through to… nothing — no other branch matches, children recursed). Then the enclosing-definition walk up node.parent (:146-156): first of class_definition | trait_definition | enum_definition | given_definition | object_definition wins. isInstanceField = class/trait/enum/given → kind field; object_definition or NOTHING (top level, package_object, braced package) → val→constant / var→variable. NOTE vs kotlin: there is NO 'local' arm — the hook never runs inside bodies (visitFunctionBody doesn't call it), so body-local vals are handled by plain recursion (§Body walker). lazy val → constant (modifiers don't matter). Extra: signature = `val|var ${name}: ${typeText}` ONLY when a type field exists (else undefined — val x = 1 has NO signature; pinned), visibility via extractVisibility (:69-80). Then emitScalaTypeRefs(typeNode, created.id) (:27-45): every type_identifier in the type subtree EXCEPT SCALA_BUILTIN_TYPES (:14-17 — Int/Long/Short/Byte/Float/Double/Boolean/Char/Unit/String/ Any/AnyRef/AnyVal/Nothing/Null) → references ref FROM THE VAL NODE at the type_identifier's position (pinned: val SHARED_TABLE: Map[String, Int] → references Map only — String/Int builtin-skipped; var cb: () => Unit → nothing). Return true → dispatcher runs scanFnRefSubtree(node, 0) and NEVER descends → top-level/class-scope property initializers emit NO calls/instantiates refs (val topInit = WidgetS.create(), val topLazy = compute(), val n = new Foo {…} → nothing — pinned) — but the SCAN still captures fn-ref candidates (§Function-refs; note the scan's nested-def halt checks functionTypes, which is EMPTY for scala, so it descends into nested function_definitions inside a hook-consumed val — it halts only at lambda_expression (tree-sitter.ts:611): val fnField = (x) => runLam(x) captures nothing, pinned extract-edge2.txt).
  2. enum_case_definitions (:173-183) — for each direct simple_enum_case | full_enum_case child: enum_member node named by the case's name field, positioned at the CASE node (so case Custom(rgb: Int) spans the params and case Earth extends Planet(5.9) spans the extends — pinned cols in extract-torture.txt). One wrapper per case line; case Red, Green = one wrapper, two cases. Return true → scanFnRefSubtree; consequences: case parameters are invisible, a case's extends_clause emits NO extends ref, and calls inside case ctor-args emit nothing.
  3. extension_definition (:186-195) — body = childForFieldName('body') then visit the body's namedChildren. Because field body is attached to EACH def (and to {/} in braced form), this is a triple quirk, all pinned (extract-ext.txt, brace-field.out):
     • paren/indent form: body = the FIRST function_definition → its CHILDREN are visited → no node is ever minted for any extension method; the first def's body expressions reach the ladder → its calls emit FROM THE ENCLOSING SCOPE (file/class) at their own positions (calls concat from=file); non-call bodies (s.length) emit nothing.
     • every def after the first is COMPLETELY invisible (never visited).
     • braced form (extension (t) { … }): body resolves to the { TOKEN → namedChildCount 0 → the whole extension is invisible (zero nodes, zero refs — extract-ext.txt ext2). Return true always (even when body lookup finds nothing).

• getSignature (scala.ts:110-117) — LIVE. params = childForFieldName('parameters'), ret = childForFieldName('return_type'); none → undefined; sig = paramsText + (ret ? : ${retText} : ''). QUIRKS, PRESERVE (pinned in extract-torture.txt):

  • Curried defs: FIRST parameter list only — def curried(a: Int)(b: String)(implicit ord: Ordering[Int]): Int → sig (a: Int): Int.
  • A def with type parameters: the TYPE param list wins — on function_definition the type_parameters node carries field name parameters and precedes the value list → def genericDef[A: Numeric, B <: BoundT](x: A): B → sig [A: Numeric, B <: BoundT]: B; def genericLeak[T](t: T): T → [T]: T.
  • No params, ret only → : Int (RichIntS::twice). Empty parens → (). Secondary ctor def this() → ().

• getReturnType = extractScalaReturnType (scala.ts:56-67) — return_type field text, trimmed: this.-prefixed (fluent this.type) → undefined; strip \[[^\]]*\] generic args (non-greedy single pass: List[Bar]→List), strip all \s, take last .-segment; must match /^[A-Za-z_]\w*$/. Pinned: : WidgetS→WidgetS; : com.example.other. Remote→Remote; : T→T (generic leak, preserve); inferred → undefined; Unit/Nothing are NOT filtered (unlike kotlin — unitRet has ret="Unit", pinned). Feeds matchDottedCallChain (§Frameworks).

• getVisibility → extractVisibility (scala.ts:69-80) — scan direct namedChildren of type modifiers OR access_modifier; TEXT .includes('private') → 'private', .includes('protected') → 'protected'; default 'public'. Kotlin-style includes-on-raw-text: private[b]/private[this] → private (pinned QualPriv). Applied to functions/methods/classes(+objects)/enums AND (via the hook) vals/vars. NOTE: in the real CST access_modifier sits INSIDE modifiers — the modifiers arm is what fires; keep both arms anyway.

• isAsync (scala.ts:121) — literally () => false: every function/method carries isAsync: false.

• isStatic (scala.ts:123-129) — modifiers text .includes('static') → scala has no static keyword → always false in practice (annotations are NOT inside modifiers in this grammar, so no kotlin-style text false positive channel — but port the text scan, not a constant).

• classifyClassNode (scala.ts:105-108) — trait_definition → 'trait', else 'class'. So object_definition → kind class (companions/case objects included) and trait → kind trait via extractClass(node, 'trait') (ladder :1014-1015 — extractInterface/ interfaceKind is DEAD code for scala).

• extractImport (scala.ts:200-211) — signature = trimmed full node text; moduleName = childForFieldName('path') text. Each dotted segment is a separate path-fielded identifier → first-match-wins → the import node/ref is named the FIRST SEGMENT: import com.example.other.OtherClass → name/ref com (pinned ×5 in extract-torture.txt; import single → single; import a.b → a). The identifier/stable_identifier fallback (:204-209) is dead (path always present). Consequence for the fn-ref gate: importedNames = {com, single, …} — imported class simple names NEVER enter the gate (unlike kotlin's last-segment rule — flushFnRefCandidates' QUALIFIED_IMPORT never sees the full path because the ref name is only the first segment).

Hooks ABSENT (the walker must NOT invent them): preParse, resolveName, recoverMangledName, isMisparsedFunction, isConst, isExported (undefined everywhere except the file node's literal false), classifyMethodNode, extractPropertyName, propertyTypes, packageTypes/ extractPackage (→ extractFilePackage returns null → NO namespace node, EVER — package headers are ignored and every top-level QN is bare; pinned), getReceiverType (no receiver-QN surface, no owner-contains fallback), resolveBody (body via the body FIELD everywhere), extractModifiers (no node.decorators), extractBareCall, synthesizeMembers, skipBodilessClass (bodiless class Foo mints a node — the :1685 comment names Scala), methodsAreTopLevel, resolveTypeAliasKind, interfaceTypes machinery.

tree-sitter.ts branches (anchors as of 45a53eb)

visitNode dispatch — what each scala node hits (ladder at 936-1303)

Node	Branch	Behavior
every node	visitNode hook first (:943)	val/var, enum_case_definitions, extension consumed; handled → scanFnRefSubtree + STOP
every node	maybeCaptureFnRefs (:990)	fires for arguments/assignment_expression/val_definition (SCALA_SPEC keys) in visitNode context too
function_definition/function_declaration	methodTypes:1027 (functionTypes EMPTY — :994 never fires)	extractMethod:1737 → gate :1747: inside class-like → method; top level (no receiver hook, no methodsAreTopLevel, parent never object/object_expression) → falls to extractFunction:1517 → function. function_declaration = bodiless def (def m(): Int in traits/abstract classes) — same routing, no body walk
class_definition	classTypes:1005 → classify	'class' → extractClass:1679. Includes case class, implicit class, abstract class
object_definition	classTypes:1005	extractClass → kind class (companion objects, case object, object X extends App)
trait_definition	classTypes:1005	classify 'trait' → extractClass(node, 'trait') → kind trait (extractInterface:1834 is UNREACHABLE)
enum_definition	enumTypes:1064 → extractEnum:1914	§Enums
type_definition	typeAliasTypes:1071 → extractTypeAlias:2890	plain type_alias node (top level AND as a class member — Outer2::Member pinned). QUIRK: the alias-value ref walk reads field 'value' → scala's field is 'type' → NO reference to the aliased type (returns false → children re-visited, nothing matches). opaque type identical
import_declaration	importTypes:1209 → extractImport:3170	§Imports
package_clause	no branch	recursed. Header form: nothing extracted, nothing pushed — contents stay file-parented with bare QNs. Braced form package a.b { class X }: recursion reaches the members (class X → file-parented, QN X — pinned extract-misc.txt). Multiple/chained package clauses likewise ignored
package_object	no branch	recursed → template_body members visited with FILE on stack: defs → extractMethod → not-class-like → functions, vals → hook (enclosingDef walk finds NOTHING — package_object is not in the list) → constants/variables; all bare-QN file children (pinned: pkgHelper function, pkgShared constant)
given_definition	no branch	recursed. given x: T = new T {…} → instance_expression child → :1255 → instantiates from the enclosing scope + (anon-body via recursion) §instance_expression row. given T = expr → expr recursed (calls emit from enclosing scope — summonOrd() pinned). No given node is ever minted; a given's name binds nothing
extension_definition	hook	§Extractor config — first-def leak / braced invisibility
call_expression (top level / template_body statements)	callTypes:1248 → extractCall:3684	class-body statements (require(size > 0) after the primary ctor, object Boot extends App { bootUp() }) attribute to the CLASS node — pinned extract-edge2.txt
instance_expression	INSTANTIATION_KINDS:1255 (:360 names scala) → extractInstantiation:4610	§Instantiation. findAnonymousClassBody:4815 looks for class_body/declaration_list — scala's anon body is template_body → null → extractAnonymousClass NEVER runs → skipChildren stays false → children recursed: the template_body's defs hit methodTypes → extractMethod → (not class-like at top level) → anon-class methods leak out as functions/methods of the ENCLOSING scope — pinned: top-level given's compare → function compare (bare QN); given-inside-object's compare/innerVal → method/field OF the object (Registry::compare, extract-given2.txt)
infix_expression	no branch	recursed; left/operator/right fields. Infix calls are INVISIBLE: list map transform, a foo b, 1 :: rest, x + y, counter += 1 emit NOTHING (no calls ref, no fn-ref — pinned)
assignment_expression	no ladder branch; SCALA_SPEC dispatch	fn-ref rhs capture (§Function-refs); children recursed (LHS field_expression reaches extractStaticMemberRef in bodies — §Static-member)
annotation	no branch (child of its definition)	consumed by extractDecoratorsFor from the decorated node (§Decorators)
lambda_expression / case_block / match_expression / for_expression / indented_block / block	no branch	recursed transparently (in bodies via visitForCallsAndStructure)
INSTANTIATION_KINDS others / impl_item / swift property / property_signature / export_statement (TS)	never	not scala node kinds; the swift property branch :1121 is language-gated

Node creation, IDs, qualified names

• createNode (:1308): id = generateNodeId(filePath, kind, name, startRow+1) = `${kind}:${sha256(`${filePath}:${kind}:${name}:${line}`).hex.slice(0,32)}`. FILE node id = file:${filePath} (:509), name = basename, qualifiedName = filePath, endLine = source.split('\n').length, isExported false.
• endLine extension via resolveBody (:1329-1334) calls the hook — ABSENT for scala → getChildByField(node, 'body')… note :1330 only calls this.extractor.resolveBody?.() — hook absent → no extension ever (scala bodies are child nodes, in-range anyway). Kernel: skip.
• contains edge from stack top for every node (:1363); extractModifiers merge (:1355) inert; captureValueRefScope (:1374) live (§Value-refs).
• buildQualifiedName (:1447-1460): stack names joined ::, file node excluded, namespacePrefix always empty. No namespace node → top-level QN = bare name even in a packaged file (pinned everywhere). Companion objects: class + object are TWO class-kind nodes with the SAME name (different start lines → different ids) and their members share one QN namespace — WidgetS::render (class) and WidgetS::create (companion) are indistinguishable by QN (pinned; no disambiguation — preserve).
• isInsideClassLikeNode (:1486): stack-top kind ∈ {class, struct, interface, trait, enum, module} — objects count (kind class), traits count, enums count.
• isClassScopeConstantAssignment (:1508): needs node.type assignment — scala's is assignment_expression → always false (Ruby-only, dead).

extractFunction / extractMethod (:1517 / :1737) — every def

Route recap: ALL defs → extractMethod first. In class-like → method node. Top level → :1747 gate fails → extractFunction (the object/ object_expression parent check :1751 never matches scala) → function node. extras (both): docstring (§Docstrings), signature (LIVE hook — §config), visibility, isAsync false, isStatic false, returnType (hook); isExported only on extractFunction path → undefined (hook absent). extractTypeAnnotations (§Type-annotation refs) then extractDecoratorsFor (§Decorators), push, body = getChildByField(node, 'body') (block / indented_block / EXPRESSION — a single-expression body like = new WidgetS(a) or = a + 1 is walked as the body; pinned instantiates from topLevel), visitFunctionBody, pop.

• Names: name field. operator defs keep the operator text as the name (+, :: — operator_identifier node; unary_- is a plain identifier; pinned method WidgetS::+). Backtick names keep backticks (class `Weird Name`/method `strange def` pinned). Secondary constructors are methods named this (def this() = this(0) → method WidgetS::this + calls ref this — pinned; the NAME_STOPLIST only applies to fn-refs, not calls).
• function_declaration (bodiless def): method node minted, sig/ret intact, no body walk (AbsS::abstractM pinned).

extractClass (:1679) — classes, objects, traits + the bodiless-header asymmetry

resolvedBody = hook(absent) ?? getChildByField(node, 'body') → template_body (braces or scala-3 colon form — same node type) / enum_body for enums. NO skipBodilessClass → bodiless mints. extras: docstring, visibility, isExported undefined. Then extractInheritance (§below) — extends refs precede member emissions. extractCsharpPrimaryCtorParamRefs — csharp-gated no-op. extractDecoratorsFor (annotations on the class — @deprecated class Old → decorates). Push, walk body children via visitNode, pop.

• Bodied class: only template_body children visited → the class_parameters (primary ctor) child is NEVER walked: ctor params mint no nodes, their types emit NO references, their default-value calls emit NOTHING (pinned: WidgetS's label: String = defaultLabel() → silent; case-class fields invisible — DataS has zero members).
• Bodiless class/object: body = the node itself (:1714) → HEADER children visited: class_parameters recursion reaches default-value call_expressions → calls from the CLASS node (pinned: case class DataS(x: Int, y: String = mkY()) → calls mkY from=class:DataS), and extends_clause arguments recursion reaches super-ctor arg calls the same way. Reproduce the asymmetry exactly. (The re-visited extends_clause emits nothing extra — extends refs come only from extractInheritance; type nodes/class_parameter children match no ladder branch.)
• Class-body members: val/var → hook (fields — or constants/variables inside OBJECTS via the enclosingDef walk, making them value-ref targets); defs → extractMethod; nested class/object/trait/enum/type_definition → their branches (QN chains pinned: Outer2::InnerObj::IC); template_body STATEMENTS (calls) → extractCall from the class (§dispatch); secondary ctor → method this.
• Traits: extractClass with kind trait — visibility IS emitted for traits (extractClass path, not extractInterface — vis="public" pinned) unlike kotlin's interface path. Trait vals → hook 'instance' → field (Drawable::traitVal pinned); bodiless trait defs → methods.
• Self-types (trait X { self: Y => … }): the self-type is invisible (no refs, no node); members extract normally (pinned extract-misc.txt).

Enums (:1914 extractEnum + hook branch 2)

body = enum_body (REQUIRED — a bodiless enum would mint nothing; doesn't occur). extras: docstring, visibility, isExported undefined. extractInheritance runs (an enum's own extends_clause). Body loop (:1941-1950): enumMemberTypes is EMPTY → every child goes through visitNode: enum_case_definitions → hook → enum_member nodes positioned at the case nodes (simple case = just the name extent; param/extends cases span their tails — cols pinned); function_definition → extractMethod (enum is class-like → Http::describe); vals → hook → fields. extractEnumMembers (:1958) is DEAD for scala. QUIRKS, PRESERVE: case parameters (Custom(rgb: Int)) and per-case extends (case Earth extends Planet(5.9)) are completely invisible — no field nodes, no extends refs, no calls from ctor args (hook consumption). Enum class_parameters (enum Planet(mass: Double)) are invisible like any bodied class's.

Imports (:3170-3236)

Hook returns {moduleName: FIRST path segment, signature: trimmed full text} → import node (name/QN = first segment) + the generic imports ref (:3183-3194): {fromNodeId: always the file node (no namespace), referenceName: first segment, line/column of the import_declaration}. No scala-specific emit pass (:3197-3234 all gated to other languages). Shapes (CST pinned in cst-snippets.txt §imports):

• import a.b.C → three path identifiers → name a.
• selectors {C, D} (namespace_selectors), wildcard _/*/given (namespace_wildcard), renames {X => Y} (arrow_renamed_identifier) / {X as Y} (as_renamed_identifier, name/alias fields) — ALL invisible: the name is still the first path segment; selectors/aliases bind nothing.
• import single (one segment) → single.
• No comment-gluing (kotlin's quirk does NOT reproduce — scala comments stay siblings; docs pinned separately).

extractCall (:3684) — the scala paths

Entry: not vbnet/erlang/ruby/arkts. func = getChildByField(node, 'function') ?? namedChild(0) (:4313) — scala call_expression HAS a real function field. cpp operator recovery :4324 gated off.

Member branch (:4364) — func.type === field_expression (in the :4364 list):

1. property = getChildByField('property') → null; getChildByField('field') → the member identifier (scala field_expression fields: value + field). The kotlin navigation_suffix fallback is dead.
2. receiver = object/operand/argument fields → all null → func.namedChild(0) = the value child.
3. LITERAL_RECEIVER_TYPES (:4397, set :373-388): scala hits string ("lit".toUpperCase()) and integer_literal (5.toString()) → emit NOTHING (pinned). Port the whole set.
4. receiver identifier (:4401) not in SKIP_RECEIVERS {self,this,cls,super} → `${recv}.${method}` (w.render, Registry.register, obj.method). this/super receivers are plain identifier nodes with those TEXTS → SKIP → bare methodName (this.mine() → mine, super.hashCode() → hashCode — pinned; unlike kotlin's this_expression path, same net effect).
5. receiver call_expression + scala in the gate (:4408-4418) → the #750 re-encode, scala arm (:4443-4464): innerFn = getChildByField(receiver, 'function') (a REAL field here — NOT kotlin's namedChild(0)) → text with ->→. then \s+ stripped; re-encode ONLY when /^[A-Z]/ (:4461) → `${innerCallee}().${methodName}`. Pinned: WidgetS.create().render() → WidgetS.create().render + inner WidgetS.create (recursion); Foo(1).bar() → Foo().bar + Foo (companion-apply chain); lowerFactory().chain() → bare chain + lowerFactory.
6. receiver field_expression (2-hop a.b.method3()) or anything else → bare methodName (pinned).

Else branch (:4518-4520) — calleeName = RAW func text: bare helper; apply-sugar WidgetS(1) → calls ref WidgetS (capitalized bare — resolution's CONSTRUCTS_VIA_BARE_CALL handles it, §Frameworks); this(0) in a secondary ctor → calls this. QUIRKS, PRESERVE (pinned):

• generic_function callee keeps its type args: genericCall[Int](1) → calls genericCall[Int] (the c/cpp <-strip :4542 is gated off and targets < anyway; deterministic garbage — reproduce byte-for-byte).
• Curried calls emit raw-text inners: curried(1)(2) → outer callee = func (a call_expression) raw text curried(1) + inner curried (recursion); Foo(1)(2) → Foo(1) + Foo (pinned extract-misc.txt).
• The parenthesized-conversion regex (:4530) applies (single-name parens rewrite) — port it.
• Final ref: {callerId = stack top, name, line = call startRow+1, column = call startColumn (UTF-16)}. Chains/args re-visited by recursion.
• Calls inside string-interpolations EMIT (in bodies): s"… ${w.render()} …" → calls w.render at the inner call's position (interpolation > block > call recursion); $id (interpolation > identifier) emits no call (pinned).
• Lambda args (xs.map(el => …) / { el => … } / partial-fn { case q => … }) — arguments node is arguments/block/case_block respectively; all recursed; inner calls attribute to the ENCLOSING function (lambdas mint nothing).

Instantiation — instance_expression (:4610, scala arm :4647-4662)

ctor = constructor/type/name fields → all null on instance_expression (only arguments is a field on it) → namedChild(0) = the type node → scalaBaseTypeName (:201-224): type_identifier/identifier → text; generic_type → recurse namedChild(0) (new Monoid[Int] → Monoid); stable_type_identifier/stable_identifier → LAST identifier segment (new a.b.C() → C); default → first direct type_identifier child ?? null. → instantiates ref at the instance_expression's position (the new). Emitted from: expression bodies (def f = new W(a) — from the function), body statements/initializers in bodies, given RHS at any scope (from file/class), ladder-visited statement positions. NOT emitted from hook-consumed val initializers (val topInit = new W(…) at top/class scope → nothing — pinned). Anonymous-class bodies: §dispatch row — never an anon class node; members leak to the enclosing scope; no extends ref to the instantiated type (extractAnonymousClass never runs).

Static-member / value-read refs (:4750-4808) — scala IS in STATIC_MEMBER_LANGS (:346)

Called ONLY from the body walker (:5218). field_expression ∈ MEMBER_ACCESS_TYPES (:327). Mechanics: callee-of-call skip (:4772-4778 — Registry.register(w)'s callee nav emits nothing); recv = object/expression/ scope fields (null) ?? namedChild(0); accepted type identifier (:4792); text /^[A-Z][A-Za-z0-9_]*$/ → references ref at the RECEIVER's position. Pinned (extract-torture.txt StaticReads):

• val c1 = Registry.count → references Registry; Http.Ok → references Http; process(Registry.count) (argument position) → references Registry (plus the process call).
• com.example.Fq.CONST_READ → NOTHING (outer recv is a field_expression; the innermost com is lowercase).
• Assignment WRITES DO emit (unlike kotlin): Registry.count = 5 — the LHS field_expression is a plain child of assignment_expression, visited by body recursion → references Registry (pinned). Preserve.
• Top-level/class-scope reads emit nothing (body walker only); hook-consumed initializers doubly so.

Decorators — scala annotations DO emit decorates, args included

extractDecoratorsFor (:4897) runs for functions/methods/classes/objects/ traits/enums (NOT hook-created vals/enum members — pinned: @volatile var → nothing). Scala annotations are DIRECT CHILDREN of the definition node (annotation node with fields name: type_identifier, arguments) — scan #1 (:4976-4978) hits them; consider() accepts type annotation (:4928); the target loop finds the type_identifier name child (:4951) → name text → <-strip + last-./::-segment normalization (:4959-4962) → decorates ref {from: decorated node, name, line/col of the ANNOTATION node}. Pinned: @main def entry → decorates main; @inline def fast → inline; @deprecated("gone", "1.0") def old → decorates deprecated (WITH-args annotations still emit — the name field precedes the arguments; kotlin's constructor_invocation dropout does NOT reproduce). Annotation ARGUMENT expressions are never visited (no calls refs from them). The modifiers-descent (:4983) and backward-sibling scan (:5013) are inert for scala (annotations are neither inside modifiers nor preceding siblings).

Inheritance — extends_clause, the scala branch (:5339-5360)

extractInheritance loops the DEFINITION node's direct namedChildren for extends_clause (field extend; a direct child on class/object/trait/enum definitions). The scala branch iterates ALL namedChildren of the extends_clause and maps each through scalaBaseTypeName → one extends ref per supertype {name, line/col of the supertype node}. Pinned:

• extends BaseW(size) with Drawable with Ordered[WidgetS] → extends BaseW + Drawable + Ordered (generic unwrapped; the arguments child yields null via the default case → skipped).
• scala-3 comma form extends B, C → both. Single extends Shape on objects (object Circle extends Shape) ✓ (pinned).
• Curried super-ctor args extends Base(1)(2) (plain, parse-clean) → extends Base only (the second arguments child → null → skipped; extract-super2.txt).
• derives Show (derives_clause, field derive) emits NOTHING — not an extends_clause; preserve the silence.
• Scala NEVER emits implements — traits ride extends.
• Enum CASE extends (case Earth extends Planet(5.9)) — hook-consumed, nothing (§Enums). Anonymous new T {…} — no class node, no extends (§Instantiation).

Type-annotation references — scala ∈ TYPE_ANNOTATION_LANGUAGES (:5753), THREE live walks + the hook's

extractTypeAnnotations (:5788) for functions/methods:

1. scala-only params walk (:5839-5842): EVERY direct parameters child (all curried lists — the trailing implicit list included) → extractTypeRefsFromSubtree (:6090): every type_identifier leaf except BUILTIN_TYPES (:5768-5782 — includes the scala block Int/Long/…/Null PLUS the cross-language entries; note lowercase error etc. can't occur) → references ref at the leaf. The type_parameters node also carries field name parameters but is NOT type parameters → not matched by this walk (it's matched by walk 3).
2. return walk (:5851): getChildByField('return_type') subtree → refs (generic return Option[A] → Option + A).
3. scala-only type-parameters walk (:5863-5870): the first type_parameters child → subtree refs — context/upper bounds emit ([A: Numeric, B <: BoundT] → Numeric + BoundT; the declared names A/B are identifier nodes → silent). Pinned order for genericDef: params-walk refs (A) → return (B) → bounds (Numeric, BoundT).
4. the type_annotation direct-child search (:5873) — no such node kind in scala → dead.

Plus the hook's emitScalaTypeRefs on val/var type ascriptions (§Extractor config — its OWN builtin set SCALA_BUILTIN_TYPES, which lacks the cross-language entries; val m: Monoid[Int] → references Monoid). extractVariableTypeAnnotation (:6074) needs a type_annotation child → dead; the body-walker variable_declarator branch (:5230) — no such kind → dead. Net: param/return/bound types on defs + ascribed val/var types emit; class_parameters types (bodied classes), local val types in bodies (no hook there, no variable_declarator), and pattern types (case ws: WidgetS) emit NOTHING. Class primary-ctor types are the notable coverage hole — preserve it.

Docstrings (tree-sitter-helpers.ts:95-127) — Scaladoc is KEPT

Scala comment node kinds: comment (//) and block_comment (/* */ and Scaladoc /** */). BOTH are in getPrecedingDocstring's accepted set (:110-115) — unlike kotlin, Scaladoc survives, and block/line runs CHAIN in either order. cleanCommentMarkers (:77-90): /*-open strip + per-line * continuation strip + // strip. Pinned (extract-docs.txt): Scaladoc → "Scaladoc kept?\nsecond line with star"; // runs joined with \n; /** block */ + // trailing → "block doc\ntrailing line"; a blank line does NOT break the chain (// detached two lines above still attaches — previousNamedSibling skips whitespace); hook-created vals get NO docstring (docVal pinned) but class/method/function/trait/enum/type_alias do. DOCSTRING_WRAPPER_TYPES contains no scala kinds → no climbing. CRLF: multi-line block comments keep a stray \r at each internal line break ("Scaladoc kept?\rsecond line with star" — pinned extract-docs-crlf.txt diff) — the JS ^/m-matches-after-\r semantics (#1329): call the shared js_multiline_strip in docstring.rs, port nothing. Line-comment runs are CRLF-clean (per-comment trim eats the \r).

Value-reference edges (:398-931) — scala IS in VALUE_REF_LANGS (:401)

Port the full machinery (crib kotlin.rs): CODEGRAPH_VALUE_REFS=0 kill; MAX_VALUE_REF_NODES 20,000; isGeneratedFile skip.

• Targets (captureValueRefScope:735): kind constant|variable, name len ≥3 AND /[A-Z_]/, parent id prefix ∈ {file:, class:, module:, struct:, enum:}. Because scala mints NO namespace node, top-level constants ARE targets (kotlin's namespace-drop quirk does NOT apply — TOP_LIMIT pinned with a class-method reader). Object/class/trait members (class: parent) are targets; count (no uppercase/underscore) is not (pinned). Same-name targets: LAST registration wins the map slot — with Config.TIMEOUT_MS and Config2.TIMEOUT_MS in one file, readers of EITHER get an edge to Config2's node (fileScopeValues.set overwrite — pinned vref2.out; wrong-target quirk, PRESERVE).
• Reader scopes: every function/method/constant/variable node (:764) — fields are NOT readers.
• Shadow prune (:803-878): the scala declarator case is val_definition/var_definition (:838-843) — pattern field, bump ONLY when the pattern IS an identifier (tuple/case-class patterns bump nothing → a destructured local shadow never prunes). bump() counts identifier nodes (:807). Every val/var ANYWHERE (the target's own declarator + body locals — the hook never sees body locals but the prune DFS does) — pinned: companion-ish Config.RETRY_MAX + method-local val RETRY_MAX = 9 → RETRY_MAX pruned (readBoth emits only TIMEOUT_MS). The kotlin/swift property_declaration case and Dart/Pascal cases are null paths here.
• Emission (:880-930): per reader scope, stack-based DFS (reverse-source-order pop — ruby precedent; edge order follows), reader node type identifier (:907 — simple_identifier/constant/name never occur in scala trees). Reads through Config.TIMEOUT_MS member positions count (the member half is an identifier). String interpolations: BOTH $CONST and ${CONST} count (interpolation > identifier / > block > identifier — pinned readInterp ×2; kotlin's $X-inert quirk does NOT apply). Skip self/same-name, dedupe per (scope,target) → EDGE {kind:'references', metadata:{valueRef:true}}, appended after the walk (§Emission order). The Dart/Pascal next-sibling pull (:891) is inert (scala bodies nest).

Function-as-value capture (#756) — SCALA_SPEC (function-ref.ts:300-308)

idTypes = {identifier} (bare identifiers ARE candidates — unlike kotlin). dispatch: arguments → args; assignment_expression → rhs field right; val_definition → varinit field value (var_definition is ABSENT — var cb = other initializers are NEVER captured, pinned extract-fnref.txt). unwrap: postfix_expression → null field → first namedChild (eta-expansion handler _ → handler, explicitRef=true). No layers/special/ungatedModes/addressOfOnly. NAME_STOPLIST applies (this, null, …).

• Capture points: ladder :990 (top-level/template statements), visitFunctionBody :5137 (body nodes), scanFnRefSubtree (hook-consumed val/enum-case/extension subtrees — the scan visits the val_definition itself at depth 0, so class/object/top-level val x = fn IS captured; the nested-def halt checks functionTypes=[] so only lambda_expression halts it — val fnField = (x) => runLam(x) captures nothing, pinned).
• Pinned channels (extract-fnref.txt, extract-fnref2.txt, extract-edge2.txt): args bare id register(handler) ✓; args eta registerEta(other _) ✓; body varinit val stored = alpha ✓; class-scope varinit val topStored = handler ✓ (from the CLASS node); assignment rhs obj.cb = beta ✓; named-argument wire(cb = cbTarget) — parses as an assignment_expression inside arguments → rhs capture ✓ (at the rhs id's position) with the param-forward skip when cb = cb (lhs tail == rhs text, :430-443); list List(delta) inside a hook-consumed val ✓ (args mode via arguments).
• NOT captured: fn.member values (field_expression — no special), infix positions (list map transform — no dispatch key), var initializers, lambda bodies under hook-consumed vals.
• Flush gate (:639-728): definedHere (same-file function/method names — a top-level def IS kind function, so register(missing) drops but same-file names pass) ∪ importedNames — which for scala is first path segments only (§Imports; effectively: cross-file callables never pass the gate). No ::/this. always-flush forms are ever produced. Dedupe ${fromNodeId}|${name} (pinned: three same-scope handler captures → one ref). referenceKind function_ref (wire code 200).

visitFunctionBody (:5129-5286) — scala rows

• maybeCaptureFnRefs (:5137) per node (assignment/varinit/args captures in bodies).
• call_expression → extractCall (:5143), children recursed after.
• instance_expression → :5145 extractInstantiation; findAnonymousClassBody → null (template_body) → NO return → children recursed → anon-body defs are NOT dispatched here (functionTypes empty, methodTypes not checked in this walker) → new Ordering[Int] { def compare … } in a body: the instantiates ref only; compare mints NOTHING and its body's calls attribute to the enclosing method (pinned).
• extractBareCall — absent.
• Nested named defs mint NOTHING (:5245 checks functionTypes — EMPTY): def innerFn(k) = … inside a body is recursed-through; its calls attribute to the ENCLOSING method (pinned: innerFn/lam/helperCall all from CallSites::localHost). This is the inverse of kotlin (which minted local fns) — preserve.
• classTypes (:5255): body-local class LocalClass/object LocalObj/trait → FULL extractClass (kind class/trait) contained by the enclosing method, members extract normally (pinned QNs CallSites::localHost::LocalClass::lm). enumTypes (:5268) likewise. typeAliasTypes NOT checked → body-local type X = … is invisible.
• extractStaticMemberRef (:5218) every node (§Static-member).
• variable_declarator branch (:5230) dead. Body-local val/var: no hook here → plain recursion → initializer calls/instantiations EMIT from the enclosing function (val local = compute() → calls compute — pinned) and no local nodes are minted. Match/for/try/if recursed transparently (case_clause pattern Some(n) emits nothing; for … yield combine(x,y) emits the call — pinned).

Misc shared paths

• Positions: line = startRow+1, column = startColumn — UTF-16 code units (pinned extract-uni.txt: 😀 counts 2, é counts 1), as are startIndex/endIndex substrings (getNodeText) and the import-signature trim.
• Refs carry NO filePath/language (§arch-5).
• extract() wrap (:454-577): file node → (no namespace) → walk → flushFnRefCandidates → flushValueRefs → pop. Table order: nodes in creation order; contains edges interleaved; value-ref EDGES appended LAST (pinned — after all contains); walk-order refs, then function_ref refs at flush (pinned last in every dump). Store/harness are rowid-order-sensitive — reproduce exactly.
• CRLF hazards inventory for the scala path: scala.ts has ONE regex over node text (extractScalaReturnType's strips — \s+ handles \r, JS/Rust parity holds) and the visibility/isStatic .includes (single-token). The shared regexes that fire: extractCall's parenthesized-conversion (:4530), decorator name normalization (:4959-4962), and cleanCommentMarkers' gm strips → js_multiline_strip in docstring.rs (#1329), call it (the block-comment \r retention is the observable — §Docstrings). Grammar CRLF probed clean (§Grammar prep). extract-torture.txt vs extract-torture-crlf.txt diff is EMPTY (torture's only multi-line comment is //-run based… its scaladoc is single-line); the docs fixture carries the multi-line pin.
• Defer policy: per-file has_error() → defer: — including phantoms (§Grammar prep (a): flag-true with zero ERROR nodes is COMMON in scala-3 code; trust the flag). wasm recovery is canonical.
• MAX_FILE_SIZE (1 MiB) / generated-file skips: shared, nothing scala-specific.

Frameworks & synthesis consumers (stay TS-side — pin the walker's output contract)

• playResolver (resolution/frameworks/play.ts) — §Architecture #2 for detection/decoded-path. Its extract() only fires on conf/routes / *.routes files (NOT .scala — they ride the no-grammar path with language 'yaml'); route nodes carry literal ids (route:${filePath}:${line}:${method}:${routePath}) and language: 'scala'; resolve() maps Controller.method handler refs via getNodesByName(className) (kind class) + getNodesInFile(cls.filePath) (kind method|function, exact name). Walker obligations: class/method node names, kinds, filePath — nothing else.
• matchDottedCallChain (name-matcher.ts:2145-2166, scala gated) — consumes the Foo.create().bar re-encode + the inner method's returnType (extractScalaReturnType's product — why Unit is left unfiltered doesn't matter here, but the last-segment/generic-strip rules do). CHAIN_LANGUAGES (resolution/index.ts:42) includes scala (the (). split).
• CONSTRUCTS_VIA_BARE_CALL (name-matcher.ts:918) — Foo(args).method() receivers resolve as class Foo (companion-apply convention).
• Local-variable receiver inference (name-matcher.ts:1197-1201) — re-reads SOURCE inside the enclosing node's span with `\bval lg = (new )?Logger` / `\blg: Logger` regexes. Walker obligations: accurate node startLine/endLine spans + language tag.
• JVM name-family (name-matcher.ts:141: scala → 'jvm') — scala refs can bind to java/kotlin nodes and vice versa; nothing extra to emit.
• NO synthesis passes are scala-gated: callback-synthesizer has zero scala mentions (CC_LANGUAGES = swift/kotlin; expect/actual kotlin-only; rnCrossPlatform NATIVE set has no scala). Generic passes (interface-impl Phase 5.5 over extends refs + method names, function_ref resolution) consume the standard tables.

Parity mechanics (all have bitten before)

• Emission order per §Misc: file → source-order walk (per construct: node + contains → extends refs BEFORE member emissions → extractor-order refs) → function_ref refs → value-ref EDGES last.
• generateNodeId inputs: (filePath, kind, name, startRow+1) — name keeps backticks (`Weird Name`) and operator glyphs (+, ::); import nodes are named the FIRST path segment; enum_member line/column = the CASE node's (which for simple cases equals the identifier); companion pairs collide on (kind,name) but differ on line. node_ids dedupe-vec pattern still required — same-(kind,name,line) CAN collide (one-line class X { … }; object X constructions, secondary-ctor this twins).
• First-match-wins field lookups over named+anonymous children — import path, def parameters, extension/for body/enumerators (§config). Implement child_by_field exactly once, tree-sitter-faithful.
• UTF-16 columns/slices (textutil::col16/slice_utf16) — pinned via uni.scala (surrogate-pair emoji counts 2).
• CRLF: variants of every fixture derived in-memory (kernel-tsjs-parity pattern); the docs fixture MUST include a multi-line /** … */ (the \r retention pin) and a Scala-3 indented file (scanner CRLF).
• Defer policy: has_error() → defer: including phantoms; sweep defaults --max-deferral 0.1 for os-lib/cats-style repos, 0.3 for scala3-style (§arch-6).

Gates (per plan §5 — NOTE: no grammar-bump gate, §Grammar prep)

• Kernel C vendor + build.rs + langs.rs + grammar-parity row land first (inert until the walker exists): GRAMMAR_LANGUAGES += 'scala' (kernel-grammar-parity.test.ts:39) must show ABI 15 / 26650 states / 32 fields / identical kind+field tables vs the production wasm.
• Torture fixtures per ## Fixtures to build, exercised by a new __tests__/kernel-scala-parity.test.ts.
• Parity sweeps (scripts/kernel-parity.mjs <dir>, order-sensitive full-object):
  • …/scratchpad/svy-scala/gate-repos/os-lib (small, 59 files, expect 0 deferrals)
  • …/gate-repos/cats (medium, 835 files, expect ~15 deferrals ≈1.8%)
  • …/gate-repos/scala3 — sweep compiler/src (577 files, ~57 deferrals ≈10%, --max-deferral 0.3) and library/src (652 files, ~116 ≈18%, the phantom-heavy set) rather than the whole repo (tests/ is deliberately-invalid input — fine for a robustness pass, useless as a parity denominator). (cloned fresh at survey; re-clone public OSS if gone — agent-eval policy.) Expect 0-diff on every NON-deferred file. Then full-init dump-diffs byte-identical (kernel arm vs CODEGRAPH_KERNEL=0, dump-graph.mjs, cmp) on all three.
• Suite: kernel-scala-parity torture + CRLF variants + .sc fixture + defer fixtures (§Fixtures 5-6) ×2 green with CODEGRAPH_KERNEL_EXPECT=1.
• DEFAULT_ROUTED += 'scala' (kernel/index.ts:37 list) only after ALL of the above; changelog rides the existing kernel entry.
• Post-route perf sanity: gate repos ride the raw path; a Play-detected repo (e.g. playframework/playframework itself) is the decoded-path smoke check.

Fixtures to build

1. __tests__/fixtures/kernel-parity/torture.scala — seed from svy-scala/torture.scala (its extract-torture.txt is the expected-output pin: 80 nodes / 82 edges / 75 refs). Inventory: package header (ignored, no namespace); imports ×5 (first-segment names; selectors/wildcards/renames); scaladoc + //-run docstrings; top-level defs (function kind) incl. curried (first-list sig), generic (type-params-first sig + bound refs), inferred/Unit/qualified/generic-leak returns, private, @main/ @deprecated(args) decorates; top-level val/var/lazy/tuple/pattern destructuring (first-identifier names) + ascribed types (refs) + initializer-invisibility; bodied class with primary ctor (params invisible), fields (val/var/private/annotated), secondary ctor (this method + this call), methods incl. operator +, member calls, extends with-chain; companion object (second class:WidgetS + shared QN space + DEFAULT_SIZE value-ref target read by both create/readDefault); case class bodiless-header asymmetry (mkY() call from class) vs bodied twin; case object extends; abstract class + function_declaration; trait with default method + val field; sealed trait + object/class extends; enum (simple/param/extends cases at case-node positions, invisible tails, method); enum with class_parameters; given → instantiates + leaked function; anonymous given; extension (first-def call leak, second-def invisibility) + single-def extension; implicit class; type aliases (no value refs) + opaque; call shapes: bare, apply-sugar WidgetS(1), member, chained cap re-encode + inner, lower chain, 2-hop, this/super bare, literal receivers (nothing), genericCall[Int] bracket callee, curried-call raw inner, new in expression body, anon new … {} in body (instantiates + leaked-nothing), interpolation call + $id, eta + bare + named-arg fn-refs, infix invisibility, match/for; static reads (Registry.count, Http.Ok, com.example.Fq.X nothing, write LHS EMITS, callee skip); local defs (innerFn invisible, LocalClass/LocalObj full); package object (flattened); UTF-16 line. Keep it parse-clean (avoid given … with {}, end identifiers, curried+generic super-args).
2. CRLF variants in-memory (kernel-tsjs-parity pattern) — plus the docs fixture's multi-line scaladoc (the \r pin) and an indented Scala-3 fixture (external-scanner CRLF — indent.scala seed, extraction byte-identical pinned).
3. .sc fixture — top-level statements → calls from FILE; file-parent value-ref target (script.sc seed).
4. given/extension/anon-class fixture — given2.scala + ext-probe.scala seeds (the leak asymmetries are the port's likeliest regression site).
5. Defer fixture #1: PHANTOM — def f(x: List[Int]^): Int = 1 — kernel defers on has_error() despite a complete, ERROR-free CST; wasm output byte-normal.
6. Defer fixture #2: real error — a given x: C with { … } or end-identifier file — kernel defers; wasm-served output pinned.
7. vref fixture — vref.scala seed: object + top-level targets, shadow prune, $X/${X} interpolation reads, lowercase non-target, the same-name last-wins mis-target (Config/Config2 TIMEOUT_MS → Config2's node).
8. fnref fixture — fnref.scala/fnref2.scala seeds: all five capture channels + var-init non-capture + dedupe + register(missing) gate drop.

Probe artifacts (session scratchpad svy-scala/)

cst-probe.cjs + snippets.json + cst-snippets.txt (20 snippet CST dumps WITH per-node childForFieldName truth tables), brace-field.out (the anonymous-token field proof: extension {-body, for enumerators), extract-probe.cjs (runs the REAL dist extractor) + ground-truth dumps extract-{torture,torture-crlf,docs,docs-crlf,vref,fnref,fnref2,misc,indent, indent-crlf,script,given2,edge2,ext,super2,imp2,uni}.txt (pinned outputs cited throughout; double as walker test expectations), vref2.out (value-ref target identity), crlf-cst.cjs (LF/CRLF s-exp equality ×7), error-sweep.cjs + errors-{os-lib,cats,scala3,scala3-compiler, scala3-library,scala3-tests}.txt, err-sample.cjs + err-samples.out (error-class contexts), errvariants.out (17 minimal shapes), phantom-scan.cjs + phantom-scan-{lib,cats}.out + phantom-min.out (the ^-postfix one-liner), fixtures (torture.scala, docs.scala, vref.scala, fnref.scala, fnref2.scala, misc.scala, given2.scala, edge2.scala, ext-probe.scala, indent.scala, uni.scala, script.sc, …), tsscala-clone/ (the 0aca5d0a6f checkout) + grammar-shas.txt, gate-repos/{os-lib,cats,scala3}. Scratch is throwaway — re-derive from this doc if gone.