Eslint breaks with: Parsing error: Cannot read property 'map' of undefined

[vfonic]

I noticed that build 4.0.0-dev.20200520 broke eslint parser (or whatever/however it's called; more info follows).

This build introduced changes that break my eslint parser as well.

TypeScript Version: (versions with ✓ work as expected)
x 4.1.0-dev.20200909 (typescript@next)
x 4.0.2 (latest release)
x 4.0.0-dev.20200520
✓ 4.0.0-dev.20200519
✓ 3.9.7

Search Terms: parsing error, eslint

Code

Here's a rather simple (one of) file that I have where parser throws error:

import React from 'react';

function useFocus(): [
  boolean,
  {
    onFocus: (e: React.FocusEvent) => void;
    onBlur: (e: React.FocusEvent) => void;
  },
] {
  const [isFocused, setFocused] = React.useState(false);

  const bind = React.useMemo(
    () => ({
      onFocus: (): void => setFocused(true),
      onBlur: (): void => setFocused(false),
    }),
    [],
  );

  return [isFocused, bind];
}

export default useFocus;

/Users/viktor/Developer/Ruby/CivicLift/app/javascript/hooks/useFocus.ts
0:0 error Parsing error: Cannot read property 'map' of undefined

EDIT: I managed to shorten this down to this tuple line:

const a = (): [boolean, boolean] => [false, true]

This is how I run this from package.json:

{
  "scripts": {
    "fix-js": "eslint --fix -c .eslintrc.js --ext .jsx,.js,.ts,.tsx app/ spec/"
  }
}

I tried running this with tsc, (node_modules/.bin/tsc -p tsconfig.json), but then useFocus doesn't come out as one of the errors. Maybe tsc skips useFocus?

Playground Link:
I don't know how to get this working in playground:
https://www.typescriptlang.org/play?noEmitHelpers=true&target=1#code/JYWwDg9gTgLgBAJQKYEMDG8BmUIjgcilQ3wG4AoczAVwDsNgJa5qBnJAMQjTYAoBKAFxwA2uThwARhAgAbVLQA04uAG8VEplx6thvJMOToYAOm1sAogDcktGPzgBeAHxwrEYABMKEzbQBCstRQegaIxKbmrNa29k6u7l4+cAC+ygC6aipoTKzwIsCsUUieinDsMMWemY7hxiZsSADKMCgwSLyYKLLs-BTZufCSwLSeTnUYDewAskggELwacALxy+q+vlrcbHpCbh5jLuVIldvsnrwwUNRI-MobfoHBu8KJh64VVZ3dvfe+KXcliJ0n8+pQJEQYMFmAUimcSmVhqN0hQUpQkAAPSCwOCeJBdaiyeCNKIUIA

Related Issues:
#38682
@weswigham had some insight into this issue?

Thank you!

[weswigham]

.elementTypes was renamed to .elements on tuples in the AST of 4.0, to account for labeled elements.

[vfonic]

I'm searching online, but I can't find much info about this.

Where should I look further?

Should I post this issue to one of eslint package repos and they would know what to do?

I searched my entire codebase and couldn't find any reference to .elementTypes.

Ok, I searched through node_modules and found which package is throwing this error.
Then I upgraded TS to latest version along with eslint and its packages and, after digging through another error, figured out a way to fix it all (had to fix @typescript-eslint/parser to v4.0.1, as v4.1.0 seems to be breaking some things).

Either way, I'm on TypeScript v4 and my eslint still works! :)

I'll close this issue as it's probably more related to @typescript-eslint/parser and they are aware of the issue.

Thanks!