fix(python): avoid receiverless subtype targets

Fixes #3396

gitnexus/src/core/ingestion/languages/python/receiver-binding.ts

@@ -45,6 +45,13 @@ function hasDecorator(fnNode: SyntaxNode, decoratorName: string): boolean {
   return false;
 }
 
+/** Static-like descriptors do not inject an instance on attribute access. */
+export function isPythonStaticLikeMethod(fnNode: SyntaxNode): boolean {
+  return (
+    fnNode.childForFieldName('name')?.text === '__new__' || hasDecorator(fnNode, 'staticmethod')
+  );
+}
+
 function firstBoundReceiverParameter(parameters: SyntaxNode): SyntaxNode | null {
   for (let i = 0; i < parameters.namedChildCount; i++) {
     const child = parameters.namedChild(i);
@@ -93,14 +100,12 @@ export interface PythonBoundReceiver {
  */
 export function classifyPythonBoundReceiver(fnNode: SyntaxNode): PythonBoundReceiver | null {
   const enclosingClass = findEnclosingClassDefinition(fnNode);
-  if (enclosingClass === null || hasDecorator(fnNode, 'staticmethod')) return null;
+  if (enclosingClass === null || isPythonStaticLikeMethod(fnNode)) return null;
 
   const functionName = fnNode.childForFieldName('name')?.text;
   // Python applies these descriptor kinds implicitly even without decorators.
   // __new__ is static-like (its class argument is explicit), while
   // __init_subclass__ and __class_getitem__ receive the class implicitly.
-  if (functionName === '__new__') return null;
-
   const params = fnNode.childForFieldName('parameters');
   if (params === null) return null;
   const parameter = firstBoundReceiverParameter(params);

gitnexus/src/core/ingestion/languages/python/subtype-dispatch.ts

@@ -1,7 +1,7 @@
 import type { ParsedFile, SymbolDefinition } from 'gitnexus-shared';
 import type { SyntaxNode } from '../../utils/ast-helpers.js';
 import { definitionIdPosition } from '../../scope-resolution/utils/definition-id.js';
-import { classifyPythonBoundReceiver } from './receiver-binding.js';
+import { classifyPythonBoundReceiver, isPythonStaticLikeMethod } from './receiver-binding.js';
 
 type PositionTuple = readonly [line: number, column: number];
 type CallShapeTuple = readonly [line: number, column: number, positionalCount: number];
@@ -81,6 +81,9 @@ function positionalCapacity(fnNode: SyntaxNode): number | undefined {
   const parameters = fnNode.childForFieldName('parameters');
   if (parameters === null) return undefined;
   const receiver = classifyPythonBoundReceiver(fnNode)?.parameter;
+  // Plain class functions still receive the instance even with no declared
+  // receiver slot. Without that slot, a zero-argument call is not proven safe.
+  if (receiver === undefined && !isPythonStaticLikeMethod(fnNode)) return undefined;
   let capacity = 0;
   let keywordOnly = false;
 

gitnexus/src/storage/parse-cache.ts

@@ -803,7 +803,9 @@ import { copyV8CacheIfPresent, tryLoadV8Cache, writeV8CacheFile } from './v8-sid
 // v118 (#3398): decorated Python methods with unproven decorator identity no
 // longer publish subtype positional capacity. Warm v117 side-channel snapshots
 // would retain that capacity and could emit a false concrete call target.
-const SCHEMA_BUMP = 118;
+// v119 (#3396): Python subtype method capacities now omit receiverless ordinary
+// methods. Warm v118 ParsedFiles would replay a false compatible target.
+const SCHEMA_BUMP = 119;
 const GITNEXUS_PKG_VERSION = (() => {
   try {
     // package.json sits at gitnexus/package.json — two levels up from

gitnexus/test/integration/resolvers/python.test.ts

@@ -1386,6 +1386,41 @@ describe('Python aliased abstract subtype method', () => {
   }, 60000);
 });
 
+describe('Python receiverless subtype method', () => {
+  it('does not emit a CALLS edge to a method that rejects the injected instance', async () => {
+    const repoDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gn-python-receiverless-subtype-'));
+    try {
+      writeFixtureRepo(repoDir, {
+        'worker.py': [
+          'class Mixin:',
+          '    def dispatch(self):',
+          '        return self.hook()',
+          'class Worker(Mixin):',
+          '    def hook():',
+          '        pass',
+        ].join('\n'),
+      });
+      const result = await runPipelineFromRepo(repoDir, () => {});
+      expect(
+        getRelationships(result, 'CALLS').filter(
+          (call) => call.source === 'dispatch' && call.target === 'hook',
+        ),
+      ).toEqual([]);
+      expect(
+        getResolutionOutcomes(result).some(
+          (outcome) =>
+            outcome.kind === 'suppressed' &&
+            outcome.filePath === 'worker.py' &&
+            outcome.name === 'hook' &&
+            outcome.reason === 'receiver-unresolved',
+        ),
+      ).toBe(true);
+    } finally {
+      fs.rmSync(repoDir, { recursive: true, force: true });
+    }
+  }, 60000);
+});
+
 // ---------------------------------------------------------------------------
 // Incomplete Python inheritance must not invent an MRO binding
 // ---------------------------------------------------------------------------

gitnexus/test/unit/incremental-parse-cache.test.ts

@@ -297,8 +297,9 @@ describe('PARSE_CACHE_VERSION', () => {
   // Moved 114 -> 115 for #3390: statically known Python call arity.
   // Moved 115 -> 116 for #3390's Python subtype-dispatch shape side-channel.
   // Moved 116 -> 117 for #3390's private positional-count side-channel.
-  it('pins SCHEMA_BUMP to 118 so concurrent bumps cannot silently collide (#2766, #3015, #3088, #2885, #3128, #2865, #3130, #1432, #3161, #3179, #3219, #3190, #3253, #3273, #3339, #3354, #3371, #2965, #3390, #3398)', () => {
-    expect(Number(PARSE_CACHE_VERSION.split('+', 1)[0])).toBe(118);
+  // Moved 117 -> 118 for #3398 and 118 -> 119 for #3396's subtype capacity correction.
+  it('pins SCHEMA_BUMP to 119 so concurrent bumps cannot silently collide (#2766, #3015, #3088, #2885, #3128, #2865, #3130, #1432, #3161, #3179, #3219, #3190, #3253, #3273, #3339, #3354, #3371, #2965, #3390, #3398, #3396)', () => {
+    expect(Number(PARSE_CACHE_VERSION.split('+', 1)[0])).toBe(119);
     expect(PARSE_CACHE_BUCKET_COUNT).toBe(128);
     // The PREVIOUS version must fail the reuse gate, not merely differ from the
     // current one — a hardcoded number outside the conflict hunk rebases cleanly
@@ -307,7 +308,7 @@ describe('PARSE_CACHE_VERSION', () => {
     for (const taken of [
       59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
       82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103,
-      104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117,
+      104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118,
     ]) {
       expect(Number(PARSE_CACHE_VERSION.split('+', 1)[0])).not.toBe(taken);
     }

gitnexus/test/unit/scope-resolution/python/python-subtype-dispatch.test.ts

@@ -174,4 +174,31 @@ describe('Python missing-member subtype argument shapes', () => {
       ),
     ).toBe('compatible');
   });
+
+  it('does not accept a receiverless ordinary method as a zero-argument instance target', () => {
+    emitPythonScopeCaptures(
+      'class Caller:\n    def dispatch(self):\n        return self.target()',
+      'caller.py',
+    );
+    emitPythonScopeCaptures(
+      'class Worker:\n    def target():\n        pass\n    @staticmethod\n    def static_target():\n        pass',
+      'targets.py',
+    );
+
+    const site = { atRange: { startLine: 3, startCol: 15, endLine: 3, endCol: 28 } };
+    const receiverless = { ...candidate(2), parameterCount: 0, requiredParameterCount: 0 };
+    const staticTarget = {
+      ...candidate(5),
+      nodeId: 'def:targets.py#5:4:Method:static_target',
+      parameterCount: 0,
+      requiredParameterCount: 0,
+    };
+
+    expect(
+      pythonMissingReceiverSubtypeCandidateCompatibility('caller.py', site, receiverless),
+    ).toBe('unknown');
+    expect(
+      pythonMissingReceiverSubtypeCandidateCompatibility('caller.py', site, staticTarget),
+    ).toBe('compatible');
+  });
 });