Child objects of a mocked instance can't access their own private fields

[mchalapuk]

Hi, I seem to be having a bit of a problem with mocked instances that have child objects that use private fields.

A short piece of code replicating the issue:

import test from "ava"
import { Mock } from "typemoq"
import * as crypto from "crypto"

class UUID {
  #uuid: string

  constructor(uuid: string = crypto.randomUUID()) {
    this.#uuid = uuid
  }
  toString() {
    return this.#uuid
  }
}

test("test mock with a private field in a child object", t => {
  const uuid = new UUID()
  t.assert(uuid.toString(), uuid.toString()) // this works

  const mock = Mock.ofInstance({ uuid })
  mock.object.uuid.toString() // this throws an error
})

The error I'm getting is the following:

I think it has something to do with how proxies are used in typemoq.

If I'm missing something, I'd appreciate if someone could direct me to a solution. Otherwise, it seems to be a big problem which needs solving. I'm happy to work on it and create a PR but I would need some direction on how to solve it.

Thanks.