[Bug]: Error when parsing ternary inside parens with arrow functions when using Flow

[nicolo-ribaudo]

💻

• Would you like to work on a fix?

How are you using Babel?

Other (Next.js, Gatsby, vue-cli, ...)

Input code

(a ? v => (sum += 1) : v => 0);

REPL

Configuration file name

No response

Configuration

No response

Current and expected behavior

It should be parsed successfully, but it throws.

Environment

@babel/parser 7.15.0

Possible solution

No response

Additional context

Originally reported at #11038 (comment)

[nicolo-ribaudo]

Another test case:

(a ? (sum += 1) : v => 0 : any)

It's a ternary type-casted to any.

Also, (a ? (sum = 1) : v => 0 : any) is ambiguous but it looks like Flow accepts it.

Another one: (a ? (sum = 1) : v => 0 : any : any) is valid; (a ? (sum += 1) : v => 0 : any : any) is not.

[lightmare]

Is there any possibility Flow/TypeScript fix their broken grammar? This mess is unsustainable.

[nicolo-ribaudo]

Flow's grammar is worse since is also has (x: T) type casts, but I don't think they'll ever change it 🤷

I also found another bug while fixing this: <T>(b => c) should throw but it doesn't.

[julianklumpers]

What is exactly fixed? I'm still getting this issue with a fresh project and d3-geo installed.

[nicolo-ribaudo]

Can you share your lockfile?

[Nefcanto]

I also got this error. I attached my package-lock.json file. However, I had to rename it to .png. Pleaes rename it back to .json

r.

[nicolo-ribaudo]

The fix was released in @babel/parser 7.15.2. You need to delete this section from your lockfile:

    "@babel/parser": {
      "version": "7.14.8",
      "resolved": "https://registry.npmjs.org/@babel/parser/-/parser-7.14.8.tgz",
      "integrity": "sha512-syoCQFOoo/fzkWDeM0dLEZi5xqurb5vuyzwIMNZRNun+N/9A4cUZeQaE7dTrB8jGaKuJRBtEOajtnmw0I5hvvA=="
    },

and re-run npm install.

[Nefcanto]

Thank you @nicolo-ribaudo for responding. I did that, but it ended up having the exact same lines of codes. In other words, it again installed 7.14.8.

[nicolo-ribaudo]

Could you try running npx nls why @babel/parser?

[Nefcanto]

Well, it seems that it was a cache problem. I completely removed package-lock.json and reinstalled everything from scratch, after a PC restart. It worked. Thank you.