nominal_typing.ts

type NatModule<Nat> = {
  
  zero: Nat;
  one: Nat;
  add: (x: Nat, y: Nat) => Nat;
};

const NatModule = <A>(cb: <Nat>(Nat: NatModule<Nat>) => A) => {
  const zero = 0;
  const one = 1;
  const add = (x: number, y: number) => x + y;

  return cb({ zero, one, add });
};

type UserModule<User extends { id: number, name: string }> = {
  make: (id: number, name: string) => User;
  name: (user: User) => string;
};
const UserModule = <A>(cb: <User extends { id: number, name: string }>(User: UserModule<User>) => A) => {
  const make = (id: number, name: string) => ({ id, name });
  const name = (user): string => user.name;

  return cb({ make, name })
};

const MyModule = UserModule(User => {
  const eduardo = User.make(1, "Eduardo");
  const x = User.name(eduardo);
  const y = eduardo.name;
});