如何在TypeScript对象迭代中根据键推断值类型

我试图在TypeScript中重写一个对象，其中值的类型取决于键.我希望TypeScript根据循环中的键缩小值的类型.以下是我的初始代码:

interface MyInterface {
  name: string;
  age: number;
  hobbies?: string[];
}

const obj: MyInterface = {
  name: 'John',
  age: 23,
};

for (const key in obj) {
  const value = obj[key];
  // TypeScript treats key as string, and value as any
  // I want it to treat value as string when key is 'name', number when key is 'age', etc.
}

在for...in循环中，TypeScript将key视为string，将value视为any.然而，我希望它在key等于'name'时将value视为string，当key等于'age'时将number视为key，当key等于'hobbies'时将string[]视为key.

我试图通过创建一个笨拙的类型生成器函数来解决这个问题，该函数生成具有类型的键值对:

function* iterateObjectTyped<T extends MyInterface, K extends keyof T>(
  obj: T
): Generator<[K, T[K]]> {
  for (const key in obj) {
    const value = obj[key as unknown as K];
    yield [key as unknown as K, value];
  }
}

for (const [key, value] of iterateObjectTyped(obj)) {
  // now TypeScript treats key as "name" | "age" | "hobbies"
  // and value as string | number | string[]
  // however:
  if (key === 'age') {
    value;
    // it still treats value as just string | number | string[]
    // even though I expected the above check to narrow down the predictions
  }
}

但这并不像预期的那样工作.尽管TypeScript现在在循环中将key视为"name" | "age" | "hobbies"，将value视为string | number | string[]，但它并没有根据if判断中的key来缩小value的类型.

有没有一种方法可以在TypeScript中实现这一点？使用TypeScript 5.4.3.任何帮助将不胜感激.