Typescript Branding and Flavoring

demo.ts

/* eslint-disable @typescript-eslint/no-unused-vars */
/* eslint-disable no-console */

/* ************************************** */

export interface Branding<BrandT> {
  _type: BrandT;
}

export type Brand<T, BrandT> = T & Branding<BrandT>;

type BrandedPersonIdEasy = Brand<number, 'BrandedPerson'>;

type BrandedPersonId = number & {
  _type: 'BrandedPerson';
};

/* ************************************** */

export type Flavor<T, FlavorT> = T & Flavoring<FlavorT>;

export interface Flavoring<FlavorT> {
  _type?: FlavorT;
}

type FlavoredPersonIdEasy = Flavor<number, 'FlavoredPerson'>;

type FlavoredPersonId = number & {
  _type?: 'FlavoredPerson';
};

/* ************************************** */

const brandedPersonId0: BrandedPersonId = 12; // error
const brandedPersonId: BrandedPersonId = 12 as BrandedPersonId;

const flavoredPersonId: FlavoredPersonId = 12;

const plainPersonId = 12;

/* ************************************** */

function logBrandedPersonId(personId: BrandedPersonId) {
  console.log(personId);
}

logBrandedPersonId(brandedPersonId); // ok
logBrandedPersonId(flavoredPersonId); // error
logBrandedPersonId(plainPersonId); // error

/* ************************************** */

function logFlavoredPersonId(personId: FlavoredPersonId) {
  console.log(personId);
}

logFlavoredPersonId(brandedPersonId); // error
logFlavoredPersonId(flavoredPersonId); // ok
logFlavoredPersonId(plainPersonId); // ok

/* ************************************** */

type SomethingOne = number;
type SomethingTwo = number;

const one: SomethingOne = 1;
const two: SomethingTwo = 2;

function logOne(x: SomethingOne) {
  console.log(x);
}

function logTwo(x: SomethingTwo) {
  console.log(x);
}

logOne(one); // ok
logOne(two); // ok

logTwo(one); // ok
logTwo(two); // ok