with infer in template string, suggestion works in 4.6, but not work in 4.7

Bug Report

🔎 Search Terms

suggestion pathof

🕗 Version & Regression Information

4.7

⏯ Playground Link

Playground link with relevant code

💻 Code

// get from https://github.com/microsoft/TypeScript/issues/20423#issuecomment-812564842
type PathOf<T, K extends string, P extends string = ""> =
  K extends `${infer U}.${infer V}`
    ? U extends keyof T ? PathOf<T[U], V, `${P}${U}.`> : `${P}${keyof T & (string | number)}`
    : K extends keyof T ? `${P}${K}` : `${P}${keyof T & (string | number)}`;


declare function consumer<K extends string>(path: PathOf<{a: string, b: {c: string}}, K>) : number;

// suggestion works well in 4.6, and not work in 4.7
consumer('b.')

🙁 Actual behavior

🙂 Expected behavior

[wwwouter]

I’m experiencing the same thing. It worked with 4.6.x, and it still works with 4.9.0-dev.20221007 and 4.8.1-rc

4.6.4

4.7.4:

It compiles fine with "id" as second argument with both versions, it seems to be the language server that is acting up.

[dmitri-gb]

We have also come across a somewhat similar case where the list of suggestions in TS 4.7 (and 4.8) is no longer the same as it was in TS 4.6.

declare function pick<T extends object, K extends keyof T>(obj: T, ...keys: K[]): Pick<T, K>;

const obj = { aaa: 1, bbb: '2', ccc: true };

pick(obj, 'aaa', ''); // suggestions inside the empty string
                      // TS 4.6: aaa, bbb, ccc
                      // TS 4.7: aaa

Playground link

It is worth noting that if I rewrite pick and make keys a proper array instead of a rest parameter, then the list of suggestions will include all the properties just as in TS 4.6.

Another way to get around the issue is to use a slightly different definition for pick:

declare function pick<T extends object, K extends (keyof T)[]>(obj: T, ...keys: K): Pick<T, K[number]>;

It’s unfortunate that the (seemingly) more natural definition of pick looses its ability to provide useful suggestions. I’m curious if this is something that the TS team would consider a regression and try to revert, or is this how we should expect things to work from now on?