TypeScript类浏览器事件系统never类型报错的简洁修复方案

我正在实现一个类浏览器的事件系统，代码定义如下：

import {Point2D} from "../src/framework/models/level";

export type EventType = keyof EventTypeMap

export type EventTypeMap = {
  click: ClickEvent
  hover: HoverEvent
}

export type CEvent = ClickEvent | HoverEvent
export type EventListener<T extends CEvent> = (event: T) => void

export type EventListenerMap = {[key in EventType]: EventListener<EventTypeMap[key]>}


export type HoverEvent = {
  type: "hover"
  position: Point2D
}

export type ClickEvent = {
  type: "click"
  position: Point2D
}

const listeners: EventListenerMap = {
  click: (event) => {},
  hover: (event) => {}
}

const onEvent = (event: CEvent) => {
  listeners[event.type](event);
}


onEvent({type: "click", position: {x: 0, y: 0}})

这是简化后的示例，onEvent函数出现了TypeScript错误：

error TS2345: Argument of type 'CEvent' is not assignable to parameter of type 'never'.
  The intersection 'ClickEvent & HoverEvent' was reduced to 'never' because property 'type' has conflicting types in some constituents.
    Type 'ClickEvent' is not assignable to type 'never'.

添加类型守卫后可以正常运行，但这种switch写法冗余（我不需要对不同事件类型做特殊处理）：

const onEvent = (event: CEvent) => {
  switch (event.type) {
    case "click":
      listeners[event.type](event);
      break;
    case "hover":
      listeners[event.type](event);
      break;
  }
}

请问有没有办法在保持函数简洁的前提下修复该错误？

可以通过以下几种简洁方式修复类型错误：

方案1：泛型约束实现精确类型推导 #

将onEvent定义为泛型函数，让TypeScript自动关联事件类型与监听函数的参数类型，同时还能严格约束入参：

const onEvent = <T extends keyof EventTypeMap>(event: EventTypeMap[T]) => {
  listeners[T](event);
};

方案2：类型断言快速兼容 #

如果不想修改函数结构，直接用类型断言告诉TypeScript当前事件与监听函数的匹配关系：

const onEvent = (event: CEvent) => {
  (listeners[event.type] as EventListener<CEvent>)(event);
};

方案3：简化类型守卫写法 #

如果偏好分支判断但不想用switch，可以用更简洁的if-else写法，比switch少冗余代码：

const onEvent = (event: CEvent) => {
  event.type === "click" ? listeners.click(event) : listeners.hover(event);
};

其中泛型方案是最优解，既保持函数简洁，又能维持严格的类型检查，避免后续扩展事件类型时出现类型漏洞。

内容的提问来源于stack exchange，提问作者Symtox