Typescript无法断言继承类型的具体实例的类型

class Animal {
  name: string;
  constructor(name: string) {
    this.name = name;
  }
}

class Dog extends Animal {
  breed: string;
  constructor(name: string, breed: string) {
    super(name);
    this.breed = breed;
  }
}

function isDog(animal: Animal): animal is Dog {
  return (animal as Dog).breed !== undefined;
}

function processAnimal(animal: Animal) {
  if (isDog(animal)) {
    console.log(animal.name + " is a dog of breed " + animal.breed);
  } else {
    console.log(animal.name + " is not a dog");
  }
}

const dog = new Dog("Buddy", "Labrador");
const cat = new Animal("Whiskers");

processAnimal(dog); // Output: Buddy is a dog of breed Labrador
processAnimal(cat); // Output: Whiskers is not a dog