TypeScript 验证类型是否完全相同的思考（Freshness 概念）

type User = {
  name: string;
};

function printUser(user: User) {
  console.log(user);
}

printUser({ name: 'Joe', email: 'joe@email.com' });
// ❌ Error: Object literal may only specify known properties, and 'email' does not exist in type 'AllowedType'.

const userData = {
  name: 'Joe',
  email: 'joe@email.com',
};

printUser(userData);
// ✅ No error

type Exact<A, B> = A extends B ? (B extends A ? A : never) : never;

type User = {
  name: string;
};

function printUser<T>(user: Exact<T, User>) {
  console.log(user);
}

printUser({ name: 'Joe', email: 'joe@email.com' });
// ❌ Error: Argument of type '{ name: string; email: string; }' is not assignable to parameter of type 'never'.

const userData = {
  name: 'Joe',
  email: 'joe@email.com',
};

printUser(userData);
// ❌ Error: Argument of type '{ name: string; email: string; }' is not assignable to parameter of type 'never'