spread operator infer to wrong type with method override and generic

[syi0808]

🔎 Search Terms

generic spread

🕗 Version & Regression Information

• This changed on version 5.3.0-dev.20231027

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.5.3&ssl=9&ssc=72&pln=10&pc=79#code/C4TwDgpgBAsg9gYwNYDECGDhwE4gOoCWwAFgBIQA2k2APDFALxQCuAdkq3AO6sB8jUABQBYAFBQoBALZgcwAPLYCAcwKs0FAFw0AKlAgAPYBFYATAM6wBMXoICUjfgAVscKQXMRdvMQ4bO0bGACDRoAJQgEHFMaJAgQOAAzWAAaKDRWEF4fUVBIKBc3Dwh4ZHRMHHwiMkpqOgE2Dm4+ARFxSRk5RRU1DU0oXX0jEwsrJht7RwLXd09vXynC2a8nQODQiKjsGLiE5Jg0jKzssTEo1nNgFmCtKABvMQkpRCRvQWfTZgoIfqXi7zSiQwWFwAH5+qVUMDKoQSOQqBBaDpeHZ+gA3OAEUyPKDPZBvD5fH7TIpzZGA6Fg34zYqQ8ogqpw2qI7yoqAYrFiAC+Age7TxSH6gkm-nuXIcaEsR25AG5TqJBJKQKwEFBEmxMAQ4KxJnyJMwbgA6AWCaSyIKCADkYDQJEtdkO5mVqtNnSC3VU6gofn4gj1EighqDiq4aCIHXNCiUno09jsOPFdjlonF9hlQA

💻 Code

type MockFactoryWithHelper<M = unknown> = (
  importOriginal:<T extends M = M>() => Promise<T>
) => Partial<Record<keyof M, any>>
type PromiseMockFactoryWithHelper<M = unknown> = (
  importOriginal: <T extends M = M>() => Promise<T>
) => Promise<Partial<Record<keyof M, any>>>

const util: {
  mock<T>(module: Promise<T>, factory?: MockFactoryWithHelper<T>): void
  mock<T>(module: Promise<T>, factory?: PromiseMockFactoryWithHelper<T>): void
} = {
  mock: (() => {}) as any
};

(async function() {
  util.mock(import('path'), async (importOriginal) => ({
    ...(await importOriginal())
  }));
})();

🙁 Actual behavior

Typescirpt throw error like Spread types may only be created from object types.(2698); on line spread syntax

🙂 Expected behavior

Typescirpt should not throw error on inline spread syntax.

Additional information about the issue

No response

[RyanCavanaugh]

The error here is because you're trying to spread a never. This is not a syntax error.

[syi0808]

The error here is because you're trying to spread a never. This is not a syntax error.

But it works well on version before 5.3.0-dev.20231027. And return value of importOriginal should never be infer as never type.

That's right. I changed the title.

[syi0808]

And if this is an unintended bug, I would love to contribute. Where can I find the changes to the 5.3.0-dev.20231027 distribution version?

[RyanCavanaugh]

every-ts can bisect to a specific commit https://github.com/jakebailey/every-ts

[syi0808]

I'll try it within a week. Thanks for sharing.

[Andarist]

Given that overloads are generally picked from the top to the bottom. Shouldn't this be fixed at the definition site of this mock method? If you swap those overloads it works OK: TS playground

Similarly, it works OK if you combine those 2 overloads into a single signature: TS playground. This solution should be preferred over the first one.

[RyanCavanaugh]

I agree with @Andarist 's comments in the PR - this doesn't seem like a bug.

[typescript-bot]

This issue has been marked as "Not a Defect" and has seen no recent activity. It has been automatically closed for house-keeping purposes.