fix(scope-resolution): mark construction-site CALLS edges in reason (opt-in), enable for Zig

PR #1432 human review, item 2: a Zig struct literal `T{ .f = x }` (no
parens) is modelled as a CALLS edge to the type — the Rust `T { .. }` /
Go `T{}` shape — and nothing on the edge told it apart from an invocation
(`get_next_spawn → SpawnRequest` from seven `return SpawnRequest{ … }`).

`ScopeResolver.markConstructionSites` (default off): when set, the edge
emitted for a `callForm === 'constructor'` site gets ` (constructor)`
appended to its reason, in both emit paths — `local-call (constructor)` /
`import-resolved (constructor)` in the free-call fallback and
`scope-resolution: call (constructor)` in the reference bridge. The Zig
resolver opts in. `Reference` gains an optional `callForm`, copied from
the site by `buildReference`, so the bridge can see the form.

Why `reason` and not a property or edge type: relationships carry no
arbitrary properties, a new column changes the relation DDL and moves
SCHEMA_FINGERPRINT, and `reason` is the channel the IMPLEMENTS `-pointer`
receiver form already uses. Why opt-in: the unsuffixed strings are a
pinned contract asserted verbatim by the other language suites
(php/cpp constructor calls expect exactly `import-resolved`); every
non-Zig edge stays byte-identical.

Tests: `references-to-edges-call-form.test.ts` pins both vocabularies
and the default-off behaviour; `zig.test.ts` asserts
`Reflect.string → Accessor` / `Reflect.url → Accessor` carry
`local-call (constructor)` next to a plain invocation, and that every
marked edge targets a Struct.

gitnexus-shared/src/scope-resolution/types.ts

@@ -24,6 +24,9 @@
 
 import type { NodeLabel } from '../graph/types.js';
 import type { SymbolDefinition } from './symbol-definition.js';
+// Type-only, so the `reference-site.ts` → `types.ts` import cycle is erased
+// at compile time.
+import type { CallForm } from './reference-site.js';
 
 // ─── §2.1 Type aliases ──────────────────────────────────────────────────────
 
@@ -752,6 +755,15 @@ export interface Reference {
     | 'import-use'
     | 'value-ref'
     | 'macro';
+  /**
+   * Call form of the site this reference was resolved from, copied verbatim
+   * from `ReferenceSite.callForm`; set only when `kind === 'call'`. The
+   * emit phase reads it to tell a construction site (`T{…}`, `new T()`,
+   * `T { .. }` — form `'constructor'`) apart from an invocation, which in the
+   * graph are both `CALLS` edges. Optional and additive: a `Reference` built
+   * without it is emitted exactly as before.
+   */
+  readonly callForm?: CallForm;
   readonly confidence: number;
   readonly evidence: readonly ResolutionEvidence[];
 }

gitnexus/src/core/ingestion/languages/zig/scope-resolver.ts

@@ -24,6 +24,12 @@ export const zigScopeResolver: ScopeResolver = {
   language: SupportedLanguages.Zig,
   languageProvider: zigProvider,
   importEdgeReason: 'zig-scope: import',
+  // A struct literal `T{ .f = x }` is a CALLS edge to the Struct node (the
+  // Rust `T { .. }` / Go `T{}` shape). Zig has no Constructor nodes, so
+  // nothing but this marker tells that edge from an invocation on the edge
+  // itself — `main → SpawnRequest` looked like a call to a function
+  // (PR #1432 review). Emits `local-call (constructor)` and friends.
+  markConstructionSites: true,
 
   loadResolutionConfig: (repoPath: string) => loadZigBuildConfig(repoPath),
 

gitnexus/src/core/ingestion/resolve-references.ts

@@ -322,6 +322,10 @@ function buildReference(site: ReferenceSite, top: Resolution): Reference {
     toDef: top.def.nodeId,
     atRange: site.atRange,
     kind: site.kind,
+    // The call form survives resolution so the graph bridge can mark
+    // construction sites (`callForm: 'constructor'`) on the CALLS edge it
+    // emits — a `Reference` otherwise keeps only the resolved def.
+    ...(site.kind === 'call' && site.callForm !== undefined ? { callForm: site.callForm } : {}),
     confidence: top.confidence,
     evidence: top.evidence,
   };

gitnexus/src/core/ingestion/scope-resolution/contract/scope-resolver.ts

@@ -878,6 +878,30 @@ export interface ScopeResolver {
    */
   readonly constructorCallTargetsClass?: boolean;
 
+  /**
+   * When true, the CALLS edge emitted for a constructor-form site
+   * (`callForm === 'constructor'`) carries ` (constructor)` appended to its
+   * `reason` — `local-call (constructor)`, `import-resolved (constructor)`,
+   * `scope-resolution: call (constructor)` — so a consumer can tell
+   * "constructs an instance of" apart from "invokes" on the edge alone.
+   *
+   * Opt-in because the unsuffixed strings are a pinned contract: the legacy
+   * DAG vocabulary (`'import-resolved' | 'local-call' | …`, see the
+   * same-graph guarantee above) is asserted verbatim by consumers and by the
+   * per-language resolver suites, constructor sites included. A language
+   * that links a construction site to the TYPE node itself — a struct
+   * literal `T{…}` in Zig, where nothing but the marker distinguishes the
+   * edge from an invocation in the schema (PR #1432 review) — opts in; the
+   * default leaves every existing edge byte-identical.
+   *
+   * The marker rides in `reason` because relationships carry no arbitrary
+   * properties (adding one moves SCHEMA_FINGERPRINT — the IMPLEMENTS
+   * `-pointer` precedent in `pipeline/run.ts`). Applies to the free-call
+   * fallback and the reference bridge; receiver-qualified construction sites
+   * are not tagged `constructor` by any provider today.
+   */
+  readonly markConstructionSites?: boolean;
+
   /**
    * How this language spells a construction expression, so the compound
    * receiver resolver can type an INLINE constructor receiver — the

gitnexus/src/core/ingestion/scope-resolution/graph-bridge/references-to-edges.ts

@@ -6,7 +6,7 @@
  *      chain looking for an enclosing Function/Method/Class.
  *   2. Resolve `toDef` → target graph-node id via `nodeLookup`.
  *   3. Emit the edge (`CALLS` / `READS` / `WRITES` / `EXTENDS` / `USES`)
- *      with the standard reason format.
+ *      with the standard reason format (`referenceEdgeReason`).
  *
  * Skips (without throwing) when either side fails to map — either side
  * may legitimately not exist as a graph node (e.g. a resolved target
@@ -36,6 +36,36 @@ import { isValueDefinitionLabel } from '../../utils/ast-helpers.js';
  */
 type ReferenceSiteSkipSet = ReadonlySet<string>;
 
+export interface EmitReferencesOptions {
+  /** When true, a constructor-form call site's edge gets ` (constructor)`
+   *  appended to its reason. See `ScopeResolver.markConstructionSites`. */
+  readonly markConstructionSites?: boolean;
+}
+
+/**
+ * `reason` of the edge a resolved reference emits: `scope-resolution: <kind>`,
+ * plus ` (constructor)` for a construction site when the provider opted in —
+ * a struct literal (`T{…}` in Zig, `T { .. }` in Rust, `T{}` in Go) or a
+ * `new T()` resolves to the type (or its constructor) as a CALLS edge exactly
+ * like an invocation does, and nothing else on the edge tells the two apart
+ * (PR #1432 review).
+ *
+ * The marker rides in `reason` because relationships carry no arbitrary
+ * properties — adding one would change the relation DDL and move
+ * SCHEMA_FINGERPRINT (see the IMPLEMENTS `-pointer` precedent in
+ * `pipeline/run.ts`). The plain `scope-resolution: call` prefix is kept, so a
+ * consumer matching the prefix still sees every call; one matching the exact
+ * string sees invocations only.
+ */
+export function referenceEdgeReason(
+  ref: Pick<Reference, 'kind' | 'callForm'>,
+  markConstructionSites: boolean | undefined,
+): string {
+  return markConstructionSites === true && ref.kind === 'call' && ref.callForm === 'constructor'
+    ? 'scope-resolution: call (constructor)'
+    : `scope-resolution: ${ref.kind}`;
+}
+
 /**
  * Value labels whose defs MAY be function-local. A reference to one of these is
  * dropped only when the def is positively identified as living inside a function
@@ -76,6 +106,7 @@ export function emitReferencesViaLookup(
    * Optional so callers that never capture bare identifiers are unchanged.
    */
   functionLocalValueDefIds?: ReadonlySet<string>,
+  options?: EmitReferencesOptions,
 ): { emitted: number; skipped: number } {
   let emitted = 0;
   let skipped = 0;
@@ -153,7 +184,7 @@ export function emitReferencesViaLookup(
         targetId: targetGraphId,
         type: edgeType,
         confidence: ref.confidence,
-        reason: `scope-resolution: ${ref.kind}`,
+        reason: referenceEdgeReason(ref, options?.markConstructionSites),
       });
       emitted++;
     }

gitnexus/src/core/ingestion/scope-resolution/passes/free-call-fallback.ts

@@ -22,6 +22,7 @@ import type {
   ParameterTypeClass,
   ParsedFile,
   Reference,
+  ReferenceSite,
   ScopeId,
   SymbolDefinition,
 } from 'gitnexus-shared';
@@ -66,6 +67,9 @@ export function emitFreeCallFallback(
     /** When true, `Type(...)` constructor calls link to the Class def
      *  itself rather than its explicit Constructor. Swift opts in. */
     readonly constructorCallTargetsClass?: boolean;
+    /** When true, a constructor-form site's edge gets ` (constructor)`
+     *  appended to its reason. See `ScopeResolver.markConstructionSites`. */
+    readonly markConstructionSites?: boolean;
     readonly isFileLocalDef?: (def: SymbolDefinition) => boolean;
     readonly isCallableVisibleFromCaller?: (ctx: {
       readonly callerParsed: ParsedFile;
@@ -621,8 +625,13 @@ export function emitFreeCallFallback(
         type: 'CALLS',
         confidence: 0.85,
         // Match legacy DAG's reason convention so consumers that
-        // assert `reason === 'import-resolved'` keep working.
-        reason: fnDef.filePath !== parsed.filePath ? 'import-resolved' : 'local-call',
+        // assert `reason === 'import-resolved'` keep working. The
+        // construction-site marker is opt-in for the same reason.
+        reason: constructionSiteReason(
+          fnDef.filePath !== parsed.filePath ? 'import-resolved' : 'local-call',
+          site,
+          options.markConstructionSites,
+        ),
       });
       emitted++;
     }
@@ -630,6 +639,19 @@ export function emitFreeCallFallback(
   return emitted;
 }
 
+/** `reason` of a free-call edge: the legacy string, plus ` (constructor)` for
+ *  a construction site when the provider opted in
+ *  (`ScopeResolver.markConstructionSites`). */
+export function constructionSiteReason(
+  base: string,
+  site: Pick<ReferenceSite, 'callForm'>,
+  markConstructionSites: boolean | undefined,
+): string {
+  return markConstructionSites === true && site.callForm === 'constructor'
+    ? `${base} (constructor)`
+    : base;
+}
+
 function siteKey(
   filePath: string,
   site: { readonly atRange: { readonly startLine: number; readonly startCol: number } },

gitnexus/src/core/ingestion/scope-resolution/pipeline/run.ts

@@ -1070,6 +1070,7 @@ export function runScopeResolution(
         {
           allowGlobalFallback: provider.allowGlobalFreeCallFallback === true,
           constructorCallTargetsClass: provider.constructorCallTargetsClass === true,
+          markConstructionSites: provider.markConstructionSites === true,
           isFileLocalDef: provider.isFileLocalDef,
           isBuiltInName: provider.languageProvider.isBuiltInName,
           freeCallsRequireInstanceOwnership: provider.freeCallsRequireInstanceOwnership === true,
@@ -1100,6 +1101,7 @@ export function runScopeResolution(
         // both correctly emit. See the build site above for why the earlier
         // allowlist could not be made safe this way.
         functionLocalValueDefIds,
+        { markConstructionSites: provider.markConstructionSites === true },
       );
   // Last-resort property resolution by workspace-unique name (A1/A5). Runs
   // after every precise pass and only sees what they left behind, so a

gitnexus/test/integration/resolvers/zig.test.ts

@@ -666,6 +666,32 @@ describe.skipIf(!zigAvailable)('Zig function-local and anonymous containers (F8)
     );
   });
 
+  it('marks a struct-literal construction site (`return Accessor{…}`) on its CALLS edge, unlike an invocation', () => {
+    // A struct literal `T{ .f = x }` (no parens) is deliberately modelled as a
+    // CALLS edge to the type — the same shape Rust `T { .. }` and Go `T{}`
+    // produce. The PR #1432 review found it indistinguishable from a real
+    // call: the marker in `reason` is what lets a consumer tell "constructs an
+    // instance of" apart from "invokes". `Reflect.string` / `Reflect.url`
+    // each `return Accessor{ .get = R.get, .set = R.set }` (reflect.zig).
+    // Same-file free-call fallback vocabulary, suffixed because the Zig
+    // resolver opts into `markConstructionSites`.
+    const calls = getRelationships(result, 'CALLS');
+    const reasonsOf = (source: string, target: string): string[] =>
+      calls.filter((e) => e.source === source && e.target === target).map((e) => e.rel.reason);
+    expect(reasonsOf('string', 'Accessor')).toEqual(['local-call (constructor)']);
+    expect(reasonsOf('url', 'Accessor')).toEqual(['local-call (constructor)']);
+    // The invocation next door keeps its plain reason: `util.helper()` in
+    // main.zig is a call, not a construction site.
+    expect(reasonsOf('main', 'helper')).toHaveLength(1);
+    expect(reasonsOf('main', 'helper')[0]).not.toContain('(constructor)');
+    // No construction site is emitted as anything but CALLS, and every other
+    // CALLS edge is an invocation.
+    const constructionSites = calls.filter((e) => e.rel.reason.endsWith('(constructor)'));
+    expect(constructionSites.map((e) => e.targetLabel)).toEqual(
+      constructionSites.map(() => 'Struct'),
+    );
+  });
+
   it('gives anonymous containers a host + ordinal identity, so no Method is ownerless and same-named fns never collide', () => {
     expect(idsIn('Struct', 'Sorter.zig')).toEqual([
       'Struct:src/Sorter.zig:Sorter',

gitnexus/test/unit/scope-resolution/references-to-edges-call-form.test.ts

@@ -0,0 +1,237 @@
+/**
+ * The CALLS edge a construction site emits must be distinguishable from the
+ * one an invocation emits (PR #1432 review, item 2).
+ *
+ * A struct literal (`SpawnRequest{ .a = x }` in Zig, `Foo { a }` in Rust,
+ * `Foo{}` in Go) and a `new Foo()` are tagged `@reference.call.constructor`
+ * by their language queries and resolve to the type (or its constructor) as
+ * an ordinary `kind: 'call'` reference. Both land in the graph as `CALLS`,
+ * and relationships carry no free-form properties (adding one moves
+ * SCHEMA_FINGERPRINT), so the call form rides in `reason` — the same channel
+ * the IMPLEMENTS `-pointer` receiver form uses.
+ *
+ * Why the assertions are exact strings: a consumer that filters by the
+ * exact `scope-resolution: call` is promised invocations only, and one that
+ * matches the prefix is promised every call. Loosening either side would
+ * silently break one of the two contracts.
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+  buildDefIndex,
+  buildMethodDispatchIndex,
+  buildModuleScopeIndex,
+  buildQualifiedNameIndex,
+  buildScopeTree,
+  type NodeLabel,
+  type Range,
+  type Reference,
+  type Scope,
+  type ScopeId,
+  type SymbolDefinition,
+} from 'gitnexus-shared';
+import { createKnowledgeGraph } from '../../../src/core/graph/graph.js';
+import type { ScopeResolutionIndexes } from '../../../src/core/ingestion/model/scope-resolution-indexes.js';
+import { buildGraphNodeLookup } from '../../../src/core/ingestion/scope-resolution/graph-bridge/node-lookup.js';
+import {
+  emitReferencesViaLookup,
+  referenceEdgeReason,
+} from '../../../src/core/ingestion/scope-resolution/graph-bridge/references-to-edges.js';
+import { constructionSiteReason } from '../../../src/core/ingestion/scope-resolution/passes/free-call-fallback.js';
+
+const FILE = 'x.zig';
+
+const range = (sl: number, sc: number): Range => ({
+  startLine: sl,
+  startCol: sc,
+  endLine: sl,
+  endCol: sc + 4,
+});
+
+const def = (nodeId: string, type: SymbolDefinition['type'], qname: string): SymbolDefinition => ({
+  nodeId,
+  filePath: FILE,
+  type,
+  qualifiedName: qname,
+});
+
+function moduleScope(ownedDefs: readonly SymbolDefinition[]): Scope {
+  return {
+    id: 'scope:m',
+    parent: null,
+    kind: 'Module',
+    range: { startLine: 1, startCol: 0, endLine: 100, endCol: 0 },
+    filePath: FILE,
+    bindings: new Map(),
+    ownedDefs,
+    imports: [],
+    typeBindings: new Map(),
+  };
+}
+
+function makeIndexes(scope: Scope, allDefs: readonly SymbolDefinition[]): ScopeResolutionIndexes {
+  return {
+    scopeTree: buildScopeTree([scope]),
+    defs: buildDefIndex([...allDefs]),
+    qualifiedNames: buildQualifiedNameIndex([...allDefs]),
+    moduleScopes: buildModuleScopeIndex([{ filePath: FILE, moduleScopeId: scope.id }]),
+    methodDispatch: buildMethodDispatchIndex({
+      owners: [],
+      computeMro: () => [],
+      implementsOf: () => [],
+    }),
+    imports: new Map(),
+    bindings: new Map(),
+    bindingAugmentations: new Map(),
+    workspaceFqnBindings: new Map(),
+    workspaceTypeBindings: new Map(),
+    namespaceFqnBindings: new Map(),
+    namespaceTypeBindings: new Map(),
+    accessibleNamespacesByScope: new Map(),
+    referenceSites: [],
+    sccs: [],
+    stats: {
+      totalFiles: 0,
+      totalEdges: 0,
+      linkedEdges: 0,
+      unresolvedEdges: 0,
+      sccCount: 0,
+      largestSccSize: 0,
+    },
+  };
+}
+
+describe('referenceEdgeReason', () => {
+  it('marks only the constructor call form; every other kind keeps the plain reason', () => {
+    expect(referenceEdgeReason({ kind: 'call', callForm: 'constructor' }, true)).toBe(
+      'scope-resolution: call (constructor)',
+    );
+    expect(referenceEdgeReason({ kind: 'call', callForm: 'free' }, true)).toBe(
+      'scope-resolution: call',
+    );
+    expect(referenceEdgeReason({ kind: 'call', callForm: 'member' }, true)).toBe(
+      'scope-resolution: call',
+    );
+    // A `Reference` minted before the field existed (or by a path that does
+    // not set it) is emitted exactly as before.
+    expect(referenceEdgeReason({ kind: 'call' }, true)).toBe('scope-resolution: call');
+    expect(referenceEdgeReason({ kind: 'read' }, true)).toBe('scope-resolution: read');
+    expect(referenceEdgeReason({ kind: 'type-reference' }, true)).toBe(
+      'scope-resolution: type-reference',
+    );
+  });
+
+  it('is opt-in: a provider that did not set `markConstructionSites` gets the pinned string', () => {
+    // The unsuffixed reasons are a contract asserted verbatim by the other
+    // language suites; the marker must not leak into them by default.
+    expect(referenceEdgeReason({ kind: 'call', callForm: 'constructor' }, undefined)).toBe(
+      'scope-resolution: call',
+    );
+    expect(referenceEdgeReason({ kind: 'call', callForm: 'constructor' }, false)).toBe(
+      'scope-resolution: call',
+    );
+  });
+
+  it('keeps the plain `scope-resolution: call` as a prefix of the marked form', () => {
+    // The compatibility promise: prefix matchers keep seeing construction
+    // sites as calls.
+    expect(
+      referenceEdgeReason({ kind: 'call', callForm: 'constructor' }, true).startsWith(
+        'scope-resolution: call',
+      ),
+    ).toBe(true);
+  });
+});
+
+describe('constructionSiteReason (free-call fallback vocabulary)', () => {
+  it('suffixes the legacy `local-call` / `import-resolved` only for an opted-in constructor site', () => {
+    expect(constructionSiteReason('local-call', { callForm: 'constructor' }, true)).toBe(
+      'local-call (constructor)',
+    );
+    expect(constructionSiteReason('import-resolved', { callForm: 'constructor' }, true)).toBe(
+      'import-resolved (constructor)',
+    );
+    expect(constructionSiteReason('local-call', { callForm: 'free' }, true)).toBe('local-call');
+    expect(constructionSiteReason('local-call', { callForm: 'constructor' }, undefined)).toBe(
+      'local-call',
+    );
+  });
+});
+
+describe('emitReferencesViaLookup — construction site vs invocation', () => {
+  it('emits both as CALLS, and only the construction site carries the constructor marker', () => {
+    // `fn get_next_spawn() SpawnRequest { helper(); return SpawnRequest{ .a = 1 }; }`
+    const caller = def('def:get_next_spawn', 'Function', 'get_next_spawn');
+    const helper = def('def:helper', 'Function', 'helper');
+    const spawnRequest = def('def:SpawnRequest', 'Struct', 'SpawnRequest');
+    const allDefs = [caller, helper, spawnRequest];
+    const indexes = makeIndexes(moduleScope(allDefs), allDefs);
+
+    const graph = createKnowledgeGraph();
+    graph.addNode({
+      id: 'fn:get_next_spawn',
+      label: 'Function' as NodeLabel,
+      properties: { name: 'get_next_spawn', filePath: FILE, qualifiedName: 'get_next_spawn' },
+    });
+    graph.addNode({
+      id: 'fn:helper',
+      label: 'Function' as NodeLabel,
+      properties: { name: 'helper', filePath: FILE, qualifiedName: 'helper' },
+    });
+    graph.addNode({
+      id: 'struct:SpawnRequest',
+      label: 'Struct' as NodeLabel,
+      properties: { name: 'SpawnRequest', filePath: FILE, qualifiedName: 'SpawnRequest' },
+    });
+
+    const invocation: Reference = {
+      fromScope: 'scope:m',
+      toDef: 'def:helper',
+      atRange: range(2, 4),
+      kind: 'call',
+      callForm: 'free',
+      confidence: 0.9,
+      evidence: [],
+    };
+    const construction: Reference = {
+      fromScope: 'scope:m',
+      toDef: 'def:SpawnRequest',
+      atRange: range(3, 11),
+      kind: 'call',
+      callForm: 'constructor',
+      confidence: 0.9,
+      evidence: [],
+    };
+    const referenceIndex = {
+      bySourceScope: new Map<ScopeId, readonly Reference[]>([
+        ['scope:m', [invocation, construction]],
+      ]),
+    };
+
+    const result = emitReferencesViaLookup(
+      graph,
+      indexes,
+      referenceIndex,
+      buildGraphNodeLookup(graph),
+      undefined,
+      undefined,
+      undefined,
+      { markConstructionSites: true },
+    );
+
+    expect(result).toEqual({ emitted: 2, skipped: 0 });
+    const edges = graph.relationships.map((r) => ({
+      type: r.type,
+      targetId: r.targetId,
+      reason: r.reason,
+    }));
+    expect(edges).toEqual([
+      { type: 'CALLS', targetId: 'fn:helper', reason: 'scope-resolution: call' },
+      {
+        type: 'CALLS',
+        targetId: 'struct:SpawnRequest',
+        reason: 'scope-resolution: call (constructor)',
+      },
+    ]);
+  });
+});