Description
Bug Report
🔎 Search Terms
KnownKeys, never, getting known interface keys
🕗 Version & Regression Information
- This changed between versions 4.3.0-beta and 4.3.1-rc
⏯ Playground Link
- 4.3.0-beta playground – types work.
- 4.4.0 playground – types fail. This issue also exists in 4.3.1-rc but that version isn't in the playground.
💻 Code
type KnownKeys<T> = {
[K in keyof T]: string extends K ? never : number extends K ? never : K
} extends { [_ in keyof T]: infer U } ? U : never;
interface HasStringKeys {
[s: string]: any;
}
interface ThingWithKeys extends HasStringKeys {
foo: unknown;
bar: unknown;
}
const demo: KnownKeys<ThingWithKeys> = 'foo';🙁 Actual behavior
demo has type never.
🙂 Expected behavior
demo has type 'foo' | 'bar'.
Other info
I'm not sure where I got KnownKeys from, but it appears on https://stackoverflow.com/a/51956054/123395.
This issue impacted https://www.npmjs.com/package/idb, but I've already worked around the issue by using the other method on that StackOverflow post. jakearchibald/idb@e3c76a5