Nominal typing with brands

brand.ts

//  Adapted from https://michalzalecki.com/nominal-typing-in-typescript/

//  see also "Flavoring" https://spin.atomicobject.com/2018/01/15/typescript-flexible-nominal-typing/

type Brand<K, T> = K & { __brand: T };

type CatalogNumber = Brand<string, 'catalogNumber'>;
type CasNumber = Brand<string, 'casNumber'>;

const pge2CatalogNumber: CatalogNumber = '14010' as CatalogNumber;
const pge2CasNumber: CasNumber = '363-24-6' as CasNumber;

//  Functions (with dummy implementations) requiring specific branded types
const validateCatalogNumber: (s: CatalogNumber) => boolean = (s) => true;
const validateCasNumber: (s: CasNumber) => boolean = (s) => true;

console.log(validateCatalogNumber(pge2CatalogNumber));
  
//  Fails to compile, incompatible types
console.log(validateCasNumber(pge2CatalogNumber));