[timurzvural]

Bug

With --checkers ≥ 3 (multi-checker pools), declaration emit of this pattern collapses current to any with no diagnostic:

// status.ts
import type { Key } from "./types";
export class StatusClass {
  RUNNING: Status = "RUNNING";
  [key: string]: Status;
}
export type Status = keyof StatusClass | "";
export const statusFromAPI: { [key: Key]: Status } = {};

// consumer.ts
import { statusFromAPI } from "./status";
export const current = statusFromAPI["RUNNING"];

Expected (and --singleThreaded / checkers 1–2): export declare const current: import("./status").Status;
Actual with ≥3 checkers: export declare const current: any;

The failure is nondeterministic with file→checker assignment: it shows up when status.ts and consumer.ts land on different checkers.

Root cause

keyof only needs index key types, but getIndexInfosOfIndexSymbol eagerly resolved index signature value types. When Status is resolved on a checker that did not already finish StatusClass via the nested success path, computing keyof StatusClass re-enters Status through the index value type. Classes always go through instantiateIndexInfos because of the implicit this type, which re-resolved deferred value types and incorrectly marked Status circular → errorType/any.

Fix

1. In getIndexInfosOfIndexSymbol, defer resolving index signature value types (leave valueType nil when a return type node exists).
2. Add Checker.getValueTypeOfIndexInfo to resolve lazily from the declaration (and apply any stored mapper).
3. In instantiateIndexInfo, keep deferred value types deferred across instantiation (store combined mapper on IndexInfo), so class this-instantiation during keyof does not reintroduce circularity.
4. Route existing .valueType reads through the lazy getter; export GetValueTypeOfIndexInfo for the API.

Tests

• New tsc/internal/compiler/declaration_checkers_64998_test.go covering checkers 1–4 against the reduced fixture.

Related

Fixes #64998

AI assistance disclosure

This PR was authored with assistance from Cursor Agent. I have read and understand the change and am prepared to discuss and revise it in review.

[Copilot]

🟡 Changes recommended

Recursive index-signature resolution can cache an in-progress sentinel as an any-flagged type without a circularity diagnostic, requiring cycle-tracking integration and negative regression tests.

1 open issue

• Report circularity instead of caching unresolved recursive index type · New

What changed in this PR

This PR addresses #64998, where declaration emit can silently replace a circular keyof alias with any depending on checker assignment.

Changes:

• Defer index-signature value resolution and preserve deferred values across instantiation.
• Route value-type consumers through a lazy getter, including API serialization.
• Add a declaration-emit regression test covering checker counts 1–4.

File	Description
tsc/​internal/​compiler/​declaration_checkers_64998_test.go	Tests declaration output across checker counts.
tsc/​internal/​checker/​types.go	Stores deferred mappers and documents cached value access.
tsc/​internal/​checker/​relater.go	Resolves index values during type comparisons.
tsc/​internal/​checker/​nodebuilderimpl.go	Resolves deferred values when building index signatures.
tsc/​internal/​checker/​nodebuilder_hover.go	Uses lazy values when comparing hover signatures.
tsc/​internal/​checker/​jsx.go	Resolves indexed JSX attribute types lazily.
tsc/​internal/​checker/​inference.go	Updates inference to use the lazy getter.
tsc/​internal/​checker/​flow.go	Resolves index values during destructuring analysis.
tsc/​internal/​checker/​exports.go	Exposes the value-resolution getter.
tsc/​internal/​checker/​checker.go	Implements deferred resolution and updates value consumers.
tsc/​internal/​api/​session.go	Resolves index values before API serialization.

_{Review effort: Balanced}

[timurzvural]

Addressed in 119d74c: deferred index value types now go through pushTypeResolution/popTypeResolution on the *IndexInfo (new TypeSystemPropertyNameIndexInfoValueType). Re-entry returns errorType without caching the in-progress sentinel, and circularity reports TS2577 on the index signature annotation. Added negative tests in circular_index_64998_test.go for direct I[string] recursion and alias-mediated recursion (index-first and alias-first), plus a control that interface Rec { [k: string]: Rec } still type-checks cleanly.