'unknown' is not assignable to type for static API with generic methods

[marikaner]

Bug Report

I am trying to have an interface (Constructable) for the static API of a class (SomeClass), which I want to be able to pass to some function (fn).
I have some static methods in the static API, that should allow to pass parameters with generic types.
I can't get the generic types to be assignable to one another.

🔎 Search Terms

'unknown' is not assignable to type

Possibly related to #45255

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about - couldn't find anything relevant

⏯ Playground Link

Playground link with relevant code

💻 Code

interface Constructable<T> {
 new (...args: any[]): T;
 myStaticMethod<P extends any>(param: P): void; // why is this treated as P extends unknown ?
}

class SomeClass {
 static myStaticMethod<P extends string>(param: P): void { }
}

function fn(ctor: Constructable<SomeClass>): void {}

fn(SomeClass);

🙁 Actual behavior

I cannot call fn with SomeClass because the generic type "'unknown' is not assignable to type string". This also does not work if I change the Constructable interface to have this method: myStaticMethod<P>(param: P): void; (generic parameter does not extend any). Then the error is simply "'P' is not assignable to type string".

🙂 Expected behavior

I expected that SomeClass is assignable to the type Constructable<SomeClass>.

[MartinJohns]

// why is this treated as P extends unknown ?

See the release notes for TypeScript 3.9: Type Parameters That Extend any No Longer Act as any, and also #29571 / #29509.

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.