Aliased optional chain calls don't narrow like their inline equivalents

🔎 Search Terms

aliased conditions control flow analysis cfa optional chain call

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.6.0-dev.20240704#code/GYVwdgxgLglg9mABAJwKYGc4BsBuqCMAFDACYBci6UyMYA5ogD6LgmrC2okCUiA3gChEiCAiqIY6AEKssXRAF4JJAPwA6WhCwg26QgCIA+gCNZXfdwDcQicETFpZnvxvDRYcVWQUvtBktJrYQBfAVCBUEhYBBQMbDwAJmJySmo-JhYwNg4wLl5BYRg7ZPVNbV0DEycLfNcRMShU7yb0gJIgxFDgoA

💻 Code

function resolve1(id: string | undefined) {
  const isBundled = id?.includes("_bundled");
  if (isBundled) {
    const str: string = id; // error
  }
}

function resolve2(id: string | undefined) {
  if (id?.includes("_bundled")) {
    const str: string = id; // ok
  }
}

🙁 Actual behavior

resolve1 errors within the if block

🙂 Expected behavior

I'd expect it to be OK. Just like resolve2 is OK with it here - the condition is exactly the same and TS supports Control Flow Analysis of Aliased Conditions and Discriminant since 4.4

Additional information about the issue

No response

リンクされた TypeScript Playground の再現コードから始め、resolve1 と resolve2 を比較します。次に、エイリアス化された条件と optional chaining の呼び出しに対する制御フロー解析を追跡します。エイリアス化された条件がインライン条件と同様に id を絞り込むことを示す回帰テストを追加または更新し、両方の文字列代入が成功することを確認します。