How to use in a library, how to use inline defined types?

[dko-slapdash]

Hi.

Two questions:

(1) In all examples, the type is first defined as a named interface (or a type) and only then its name is passed to assertTypeFn:

interface Person {
  name: string;
}
const assertPerson = assertTypeFn<Person>();
assertPerson(json).unwrap();

Is it intentional that it doesn't work with anonymous types?

const assertPerson = assertTypeFn<{ name: string; }>();  // <-- does not work
assertPerson(json).unwrap();

(2) I haven't found any way to pass the type via a generic parameter to some library function:

// json-request.ts
export async function jsonRequest<TRes>(url: string) {
  const json = await fetch(url); // do some more magic there too, like logging
  const asserter = assertTypeFn<TRes>();
  return asserter(json).unwrap(); // <-- does not work
}

// some-file.ts
import { jsonRequest } from "json-request";
...
const res = await jsonRequest<{ 
  name: string;
  age?: number;
}>("https://example.com");
// I want res here to be (a) strongly typed and (b) validated at run-time

Probably it's expected, because TS transformer works locally and doesn't trace the callers. My question here is - how do I express something similar to this? Because the above syntax (some-file.ts) is basically the essence of what's needed in 99% of the cases... especially in the code which sends lots of different requests, and each request is mentioned there only once (so it makes no sense to create a named type for its response structure).