在下面的例子中，为什么 `fleet: vehicle3` 不抛出错误？

Question

试图弄清楚generics。

我的理解是const friday:Transport<Car> 将T 设置为Car。

鉴于 vehicle3 是 Bike 类型，为什么 TypeScript 不抛出错误？

'use strict';

interface Vehicle {
  brand: string;
}

interface Bike extends Vehicle {}

interface Car extends Vehicle {}

interface Transport<T> {
  fleet: T;
  manager: string;
}

const vehicle1: Car = {
  brand: 'Honda',
}

const vehicle2: Car = {
  brand: 'Toyota'
}

const vehicle3: Bike = {
  brand: 'Specialized'
}

const today:Transport<Car> = {
  fleet: vehicle1,
  manager: 'Cindy'
};
const tomorrow:Transport<Car[]> = {
  fleet: [vehicle1, vehicle2],
  manager: 'John'
}
const friday:Transport<Car> = {
  fleet: vehicle3,
  manager: 'Steve'
}

编辑

正如 Alexey 所指出的（谢谢！），TypeScript 接口是 structural，因此以下行为符合我的预期，因为 Car 和 Bike 具有冲突的属性。

'use strict';

interface Vehicle {
  brand: string;
}

interface Bike extends Vehicle {
  rider: string
}

interface Car extends Vehicle {
  driver: string
}

interface Transport<T> {
  fleet: T;
  manager: string;
}

const vehicle1: Car = {
  brand: 'Honda',
  driver: 'Alex'
}

const vehicle2: Car = {
  brand: 'Toyota',
  driver: 'Bob'
}

const vehicle3: Bike = {
  brand: 'Specialized',
  rider: 'George'
}

const today:Transport<Car> = {
  fleet: vehicle1,
  manager: 'Cindy'
};
const tomorrow:Transport<Car[]> = {
  fleet: [vehicle1, vehicle2],
  manager: 'John'
}
const friday:Transport<Car> = {
  fleet: vehicle3,
  manager: 'Steve'
}

Answer 1

这可以简化为

const v4: Car = vehicle3

TypeScript 接口是结构化的，所以Vehicle、Car 和Bike 都是相同的。见Type Compatibility。