如何限制typescript的文字表达式只接受可用的属性？

const obj: { name: string; age: number } = { name: "Alice", age: 20 };

// 使用尖括号语法进行类型断言
const nameLength1 = (obj as { name: string }).name.length;

// 使用as关键字进行类型断言
const nameLength2 = (obj as { name: string }).name.length;

function isString(value: unknown): value is string {
  return typeof value === "string";
}

function printLength(value: unknown) {
  if (isString(value)) {
    console.log(value.length);
  }
}