Design Meeting Notes, 2026-09-15

まだ誰も着手していません。

# Better Type Inference Self-Referential Values

- https://github.com/microsoft/TypeScript/issues/64192
- https://github.com/microsoft/TypeScript/issues/62180
- https://github.com/microsoft/TypeScript/issues/62181
- https://github.com/microsoft/TypeScript/pull/64172
- https://github.com/microsoft/TypeScript/pull/64248

```ts
const Category = z.object({
get subcategories() {
// ~~~~~~~~~~~~~
// Subcategory implicitly has type 'any' because of circular
// resolution.
return z.array(Category);
}
});
```

* Zod and similar libraries are motivation here.
* While processing the object literal, we normally defer return types for `get` accessors.
* But when validating the constraint, we start pulling on those very types.
* One idea: when we try to resolve a call that is already undergoing resolution, we say "don't check constraints".
* Why don't we disable constraint checking for all calls and do it in another pass?
* We're not always interested in just generating an error, we're often trying to grab the constraint for other information (e.g. if there's no candidates, we have to fix to the constraint).
* How does this affect overloads? Because this would affect how we choose overloads, right?
* Should not play in?
* Could we just return the original *uninstantiated* type parameter from the call when you detect this circularity?
* How would that work? Isn't that a type parameter leak?
* Yes, but the idea is there's an "outer" call and an "inner" call. The inner call would leak a type parameter (e.g. `T`) and the outer call would instantiate it after inference.
* Scary, but maybe!
* Outstanding PRs are likely not quite what we're looking for, but may have a PR prototyping these ideas soon.

まずリンクされている issue 64192、62180、62181 を読み、その後、既存のアプローチを確認するために PR 64172 と 64248 をレビューしてください。メモでは、循環型推論、overload、constraints、型パラメーターの漏洩に関する未解決の設計がいくつか検討されていますが、ファイル、テスト、完了基準は特定されていません。

索引モデルが issue の本文から書いたものです。