TS5115 in published Zod 4.5–4.6 types after #64372 #64605

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1. Ryan Cavanaugh (RyanCavanaugh)

   added

   Needs InvestigationThis issue needs a team member to investigate its status.This issue needs a team member to investigate its status.

   on Oct 6, 2026
2. Ryan Cavanaugh (RyanCavanaugh)

   added this to the TypeScript 7.1.1 RC milestone on Oct 6, 2026
3. Ryan Cavanaugh (RyanCavanaugh)

   assigned

   Gabriela Araujo Britto (gabritto)

   on Oct 6, 2026
4. RedesignedRobot commented on Oct 8, 2026

   

   Amir Ayub (RedesignedRobot)

   on Oct 8, 2026

   More actions

   I traced this one while checking Zod 4.6.5 on the 7.1 nightlies.

   Cause: #64372 stopped resolveObjectTypeMembers from storing declared members before the base types resolve. When a base type argument refers back to the type, member resolution starts over and instantiates the same bases again until the depth limit.

   In Zod, $ZodRecordInternals<ZodString, ZodJSONSchema> has $InferZodRecordInput in its base type arguments. That reads optin through IsOptionalIn over the union members, which leads back to $ZodRecordInternals<ZodString, ZodJSONSchema> itself. But that type declares optin, and addInheritedMembers never replaces a declared value member, so the answer is known before the bases resolve. The cycle isn't real. The reduction above reaches the same point through isStringIndexSignatureOnlyType.

   A fix that keeps what #64372 guarantees: while resolveObjectTypeMembers adds inherited members, keep the type's declared members on a small stack. In that window:

   • getPropertyOfTypeEx returns a value member the type declares itself, the same symbol the resolved members end up holding
   • isStringIndexSignatureOnlyTypeWorker returns false for a type that declares a property

   Every other query resolves the members again, as it does today, and nothing partial is stored on the type. It's 54 lines in checker.go.

   Results at 673a5f1:

   • the reduction above, and zod@4.6.5 with z.json() in arrays, records, unions, tuples, maps and .pipe(), with skipLibCheck on and off: all clean
   • TestLocal, the fourslash tests (including TestNoGhostErrors) and the checker tests pass
   • one baseline moves: mutuallyRecursiveInference.errors.txt loses the TS5114 that Restore idempotency to resolveObjectTypeMembers #64372 added. I think that one was a false cycle too, since X[X['a']] only reads members X declares. keyofGenericExtendingClassDoubleLayer keeps its TS5115.

   Happy to open a PR if this direction works for you.
5. rsnodgrass commented on Oct 9, 2026

   

   Ryan (rsnodgrass)

   on Oct 9, 2026

   Last edited by rsnodgrass

   More actions

   Confirmed that this still reproduces with typescript@7.1.0-dev.20261009.1 and zod@4.6.5, using a minimal standalone project. The same project passes with typescript@7.0.2.

   index.ts:

   import * as z from 'zod';
   
   const item = z.object({ data: z.json() });
   
   export const value: z.infer<typeof item> = { data: 1 };

   tsconfig.json:

   {
     "compilerOptions": {
       "strict": true,
       "noEmit": true,
       "module": "preserve",
       "moduleResolution": "bundler",
       "target": "esnext",
       "skipLibCheck": true
     },
     "files": ["index.ts"]
   }

   Running tsc -p . --pretty false with the nightly produces:

   index.ts(5,44): error TS5115: Instantiations of the following types appear infinitely circular: '$ZodTypeInternals', '$InferZodRecordInput', 'IsOptionalIn'.
   

   Zod	TypeScript 7.0.2	TypeScript 7.1.0-dev.20261009.1
   4.3.6	Pass	Pass
   4.6.5	Pass	TS5115

   The version comparison is for this reproduction only. It independently confirms the affected-version range already reported here; it does not establish that every older-version schema is unaffected.

   The Rust port also tracks this upstream regression in pingdotgg/ts-rust#20. Adding this nightly confirmation here rather than opening a duplicate.

   Tobias Fu (@realtobyfu), please review the standalone reproduction and version comparison above.