/**
 * @description Makes a subset of properties K in type T required, while keeping others as they are.
 * @template T The original type.
 * @template K A union of keys from T that should be made required.
 */
type MarkRequired<T, K extends keyof T> = T & { [P in K]-?: T[P] };

// --- Usage Example ---
interface User {
  id: string;
  name?: string;
  email: string;
  age?: number;
}

// UserConfig will have 'name' and 'age' as required, 'id' and 'email' remain required.
type UserConfig = MarkRequired<User, 'name' | 'age'>;

const user1: UserConfig = {
  id: '123',
  name: 'Alice',
  email: 'alice@example.com',
  age: 30, // Required
};

// This would cause a type error because 'name' and 'age' are required
// const user2: UserConfig = {
//   id: '456',
//   email: 'bob@example.com',
// };