/**
 * Creates a new type by taking an existing type T,
 * and making a specified subset of its properties (K) required.
 * Properties in K must exist in T and be optional initially.
 */
type WithRequired<T, K extends keyof T> = T & { [P in K]-?: T[P] };

interface UserProfile {
  id: string;
  name: string;
  email?: string;
  phone?: string;
  address?: {
    street: string;
    city: string;
  };
}

// Example 1: Make 'email' required
type UserProfileWithRequiredEmail = WithRequired<UserProfile, 'email'>;

const user1: UserProfileWithRequiredEmail = {
  id: 'u1',
  name: 'Alice',
  email: 'alice@example.com', // Must be provided
};

// const user2: UserProfileWithRequiredEmail = { // Type Error: Property 'email' is missing
//   id: 'u2',
//   name: 'Bob',
// };

// Example 2: Make 'email' and 'phone' required
type UserProfileWithRequiredContact = WithRequired<UserProfile, 'email' | 'phone'>;

const user3: UserProfileWithRequiredContact = {
  id: 'u3',
  name: 'Charlie',
  email: 'charlie@example.com',
  phone: '123-456-7890',
};

// const user4: UserProfileWithRequiredContact = { // Type Error: Property 'phone' is missing
//   id: 'u4',
//   name: 'David',
//   email: 'david@example.com',
// };

console.log('--- WithRequired Demo ---');
console.log(user1);
console.log(user3);