I have this:

const any = (any?: any): any => any;

export type Fn = (cb: (...args: (string | number)[]) => any) => any;

const Fn: Fn = any();

const t1 = Fn((x: unknown) => x); // Allowed
const t2 = Fn(<X>(x: X) => x); // Allowed

How can i disallow unknown parameters inside the callback?

I have tried:

• Setting strictFunctionTypes inside tsconfig.json
• Using an Exact utility type
• Using a generic on the cb declaration

None of these have worked for me so far.
So, how do I avoid callbacks without constrained arguments.

Here is what should be allowed:

const t3 = Fn((a: string, b: number) => {});
const t4 = Fn(() => {});
const t5 = Fn((x: string | number, y: string) => {});
const t6 = Fn(<X extends number>(x: X) => x);
const t7 = Fn(<X extends string, Y extends string>(x: X, y: Y) => x + y);

Currently most of these don’t work either…
How can I solve this issue?

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