Sometimes, keyof any is string

[AFatNiBBa]

🔎 Search Terms

keyof any string

🕗 Version & Regression Information

Tested in the playground on "v3.3.3333" and "Nightly", it occurs in both versions

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.8.0-dev.20250217#code/FAFwngDgpgBA8gIwFYwLwwN4wNoGsYCWAdjLlGAPYBmMAhkWALoBcMRArgLYJQBOMAX2AB6YTHEA9APzBQkWAGlyAZzSly1eMgDcIsZJnAAJlADGAG1q9YpikWUgYFZK0RJdzpNgDKYbhXMAOgIQPloQCl5GGFEYAAoAFQALAlUEa1pcZQBKIA

💻 Code

type Obj = { [k in keyof any]: number }
//   ^? type Obj = { [x: string]: number; }

type Keys = keyof Obj;
//   ^? type Keys = string | number | symbol

declare const obj: Obj;
obj[Symbol.iterator] // (This breaks)

🙁 Actual behavior

The Obj type allows indexing only with strings

🙂 Expected behavior

The Obj type should allow indexing with every type of property key

Additional information about the issue

No response

[mkantor]

I came across a relevant comment that may be of interest to anyone looking at this issue.