Broken IndexedDB event typings in 3.1.5

TypeScript Version: 3.1.5

Search Terms:
indexedDB

Code

let dbreq = indexedDB.open('test', 1);

dbreq.onsuccess = function (evt) {
    let database = evt.target.result;
}

Expected behavior:
evt.target.result should be an IDBDatabase

Actual behavior:
TS2339: Property 'result' does not exist on type 'EventTarget'.

Playground Link:
http://www.typescriptlang.org/play/index.html#src=let%20dbreq%20%3D%20indexedDB.open('test'%2C%201)%3B%0D%0A%0D%0Adbreq.onsuccess%20%3D%20function%20(evt)%20%7B%0D%0A%20%20%20%20let%20database%20%3D%20evt.target.result%3B%0D%0A%7D

Related Issues:
This is caused by the updates resulting from https://github.com/Microsoft/TypeScript/issues/25547

It works if you add a cast:

let dbreq = indexedDB.open('test', 1);

dbreq.onsuccess = function (evt) {
    let database = (evt.target as IDBOpenDBRequest).result;
}

从 TypeScript 3.1.5 中涉及 IndexedDB 事件回调的 DOM 类型定义开始，使用 Playground 链接重现错误。阅读相关 issue #25547 以了解之前的更改，然后验证示例是否能在不使用 cast 的情况下将 evt.target.result 识别为 IDBDatabase。