(event: TouchEvent) => void is not assignable "touchstart" event.

[Glinkis]

TypeScript Version: 2.8.0-dev.20180314

Code

const onTouchStart = (event: TouchEvent) {}
document.addEventListener("touchstart", onTouchStart);

Expected behavior:
onTouchStart should be treated as an event listener.

Actual behavior:

Argument of type '(event: TouchEvent) => void' is not assignable to parameter of type 'EventListenerOrEventListenerObject'.
  Type '(event: TouchEvent) => void' is not assignable to type 'EventListenerObject'.

Playground Link: link
Though the playground does not really demonstrate the issue, as it's not on the newest typescript version.

[RyanCavanaugh]

Doesn't repro for me on latest. Are you passing any commandline flags as well?

[Glinkis]

No, just running it normally after updating to the latest @next.

[timocov]

@RyanCavanaugh

we have the same errors in our project with 2.8. Steps to reproduce is very simple:

1. mkdir test && cd test
2. npm install typescript@2.8-rc
3. ./node_modules/.bin/tsc --init
4. touch file.ts
5. Insert the following code into file.ts:

   declare function onTouchStart(event: TouchEvent): void;
   document.addEventListener('touchstart', onTouchStart);

6. ./node_modules/.bin/tsc

As result:

file.ts(2,41): error TS2345: Argument of type '(event: TouchEvent) => void' is not assignable to parameter of type 'EventListenerOrEventListenerObject'.
  Type '(event: TouchEvent) => void' is not assignable to type 'EventListenerObject'.
    Property 'handleEvent' is missing in type '(event: TouchEvent) => void'.

[MaceWindu]

The reason of it is that typing of touch events changed in lib.dom.d.ts from TouchEvent to Event.
by this commit: 67c7b36#diff-46fd87925e4552c166ec188712741c3f

[mhegazy]

PRs welcomed. You can find more information about contributing lib.d.ts fixes at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes.

[jakearchibald]

Created a PR microsoft/TypeScript-DOM-lib-generator#394.

This is a pretty big regression and it doesn't seem easy to work around. Feels like 2.8 shouldn't ship without a fix.