Spurious missing Symbol.iterator on never when yield*ing generic call within a generic call

[Andarist]

🔎 Search Terms

iteration yield iterator symbol generic call inference

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.9.0-dev.20250228#code/CYUwxgNghgTiAEYD2A7AzgF3gSxSkMAXPAN4BQ88APAIIB8AFAG5QQCuIxNAlMeZZQa94NANwUBAbQDKATwC2AIyQQAdNgwEoGJDAC6QvhIHx8ADwwNV12AHM0xAEogowVBFk0YMKLKpQUWTphAElNHx0YZzQ2CAx-QIAaETpxEwBfNPhMshyyUEhYBAAzNhQwDGxUeCQ2cNpGZWBZYmZWDi5ueABeOngAcRB8CN0E2WSA8fhJ4OImJGxgcTJa8IZS8srUACpqABVGFnZOeD2u-kRUTHg4GLie+FlsEAhgXdxhtuPuUXgAej+8AIMF0AH5cj8yCs6gR1mUKlUULsqAcvh1TucJMh0FgzA8PrCjhxIZRsddbrEsN1Hs9XrszL8ATUANYQ0RAA

💻 Code

declare const inner: {
  <A>(value: A): {
    (): A;
    [Symbol.iterator](): {
      next(...args: ReadonlyArray<any>): IteratorResult<any, A>;
    };
  };
};

declare function outer<A>(body: (value: A) => Generator<any, any, any>): void;

outer(function* <T>(value: T) {
  const result = yield* inner(value); // error?
});

outer(function* <T>(value: T) {
  const x = inner(value);
  const result = yield* x; // ok
});

🙁 Actual behavior

It errors on the first inner call with a spurious error

🙂 Expected behavior

it shouldn't error, both calls to inner are the same here - the second one that happens outside of the yield* context works just OK

Additional information about the issue

This signature is crafted based on the problem diagnosis. The original issue can be seen in a better example here: TS playground