How to return a specific method type through a proxy function?

Question

JavaScript

I have a set of classes, from one parent. All methods return the same types, for each method.
There is a f-tsya driver which, according to some logic, decides from which class to call the method passed in the argument.

As a result, driver returns a mix of types to call any argument.
The question is how to show ts that by passing the `getString` argument - I want to get the type string in the stringResult variable

Implementation attempt

interface ParentI {
  getString: () => string;
  getNumber: () => number;
  getBoolean: () => boolean;
}

class Parent implements ParentI {
  getString() {
    return 'test';
  }

  getNumber() {
    return 2;
  }

  getBoolean() {
    return true;
  }
}

class ChildrenA extends Parent {
  getString() {
    return 'first';
  }

  getNumber() {
    return 2;
  }
}

class ChildrenB extends Parent {
  getString() {
    return 'second';
  }

  getNumber() {
    return 2;
  }
}

type R = keyof ParentI;

class Driver {
  childrenA = new ChildrenA();
  childrenB = new ChildrenB();

  resolveMethod(methodName: R) {
    const random = Math.random();
    if (random > 0.5) {
      return this.childrenA[methodName]();
    } else {
      this.childrenB[methodName]();
    }
  }
}

const driver = new Driver();
const stringResult = driver.resolveMethod('getString'); // тут возвращается (string | number | boolean) - надо только (string)
const numberResult = driver.resolveMethod('getNumber'); // тут возвращается (string | number | boolean) - надо только (number)
const BooleanResult = driver.resolveMethod('getBoolean'); // тут возвращается (string | number | boolean) - надо только (boolean)

Answer 1

https://www.typescriptlang.org/play?jsx=0&module=1...