See code below StackBlitz

I can’t figure out how to make typescript infer the return type correctly. It’s supposed to be an object with a results property, but instead, it’s never.

You can tell by the error in the 2nd argument that it’s able to infer the parameters just fine, or it wouldn’t complain about the string argument where a number is expected.

import { Client } from '@hubspot/api-client';

type GetReturnType<T> = T extends (...args: unknown[]) => Promise<infer U> ? U : never;
type GetParameters<T> = T extends (...args: infer U) => unknown ? U : never;

async function call<T extends 'crm', U extends keyof Client[T], V extends keyof Client[T][U], W extends keyof Client[T][U][V]>(
  method: [api: T, entity: U, apiSection: V, method: W],
  ...args: GetParameters<Client[T][U][V][W]>
): Promise<GetReturnType<Client[T][U][V][W]>> {
  [method, args]

  return undefined as any
}

const res = await call(
  ['crm', 'companies', 'basicApi', 'getPage'],
  'test', // correctly shows error because it should be number
  undefined,
  ['city'],
);

res.results; // res is `never`. I don't understand why.