type User = {
  id: number;
  name: string;
  role?: 'admin' | 'user';
};

function processUser(user: Partial<User>): string {
  const defaultUser: User = {
    id: 0,
    name: 'Guest',
    role: 'user'
  };
  
  const mergedUser = { ...defaultUser, ...user };
  
  if (mergedUser.role === 'admin') {
    return `Admin: ${mergedUser.name}`;
  }
  
  return `User: ${mergedUser.name} (ID: ${mergedUser.id})`;
}

console.log(processUser({ name: 'John', role: 'admin' }));