Change return type of `Object` call signature to `unknown` (currently `any`)

🔎 Search Terms

ObjectConstructor, Object, assignable, function

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about 5.3.3

⏯ Playground Link

https://www.typescriptlang.org/play?#code/CYUwxgNghgTiAEAzArgOzAFwJYHtVJxwAowAjALniIEp4BeAPngGcMYtUBzaygNxyzAA3ACgRiQjSEB6afECg5PACiADwAO4DCGDw4zZBAyUQMGDhjjJNekwBEt6jLmLVGzNt0h9hyqhzwTMwsJYmtGeFQDCEdZBWV1TQ89AyMA03NLYgBvAF9qWJcE9x1knzSgzKIAZTYObic410SSrxTff0CMkKIAOWQAW1ITGOd4ty0W71TOi0qAeVIAK00R+EAZcjHmzynjdIsgA

💻 Code

declare function foo(cb: () => string): void;

foo();// ✅ Expected result: error
foo(() => "");// ✅ Expected result: no error
foo(() => null);// ✅ Expected result: error
foo({})// ✅ Expected result: error
foo(String);// ✅ Expected result: no error
foo(Number);// ✅ Expected result: error

foo(Object);// ❌ Expected result: error

🙁 Actual behavior

Object (ObjectContructor) is assignable to any function, because it has a callable signature with return type of any.

This lets the developers to use Object where only a properly typed function would be allowed, which can lead to unexpected runtime errors.

I know this is a pretty edge case, but in my opinion it's worth looking into.

🙂 Expected behavior

Object is not assignable to functions with different return type

Additional information about the issue

No response

Start with the linked TypeScript Playground example and the ObjectConstructor call signature described in the issue. Check how changing its return type from any to unknown affects assignability, then verify that Object is rejected for the shown string-returning callback while the other examples retain their expected results.