TypeScript switch-case穷举检查不起作用？

Question

const changeToInvalidations = (change: Change): Array<Invalidation> => {
  switch (change.resourceType) {
    case "brand":
      switch (change.type) {
        case "added":
          return [{ type: "page", value: "productListing" }]
        case "updated":
          return [{ type: "brand", value: change.resourceId }]
        case "removed":
          return [{ type: "brand", value: change.resourceId }]
      }
    case "product":
      switch (change.type) {
        case "added":
          return [{ type: "page", value: "productListing" }]
        case "updated":
          return [{ type: "product", value: change.resourceId }]
        case "removed":
          return [
            { type: "page", value: "productListing" }, // pagination reflow
            { type: "brand", value: change.resourceId },
          ]
      }
  }
}

Change类型的定义：

type Change = {
  type: "added" | "updated" | "removed"
  resourceId: number
  resourceType: "brand" | "product"
}

错误：

  

函数缺少结束return语句，返回类型不包括＆＃39; undefined＆＃39;

但是从阅读https://www.typescriptlang.org/docs/handbook/advanced-types.html

开始

看来我应该好好去。我做错了什么？

Answer 1

错误消息可能是指缺少default:的情况，其中没有定义return语句。如果resourceType或type属性为undefined，则会切换为default个案。