Nullish Coalescing Operator (??) #680

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: https://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
    • Replacing all ?? with || does not suffice, and causes errors
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages
    • Close, but does weird highlighting on large files: https://atom.io/packages/language-javascript-jsx

Description

Atom does not take ?? (Nullish Coalescing Operator) into account when highlighting/folding

Steps to Reproduce

1. Use the JavaScript syntax highlighter
2. Copy/Paste

// ...
// Notifications
NOTIFICATIONS = $('[data-test-selector="onsite-notifications-toast-manager"i] [data-test-selector^="onsite-notification-toast"i]', true).map(
    element => {
        let streamer = {
            live: true,
            href: $('a', false, element)?.href,
            icon: $('figure img', false, element)?.src,
            name: $('figure img', false, element)?.alt,
        };

        if(!defined(streamer.name))
            return;

        element.setAttribute('draggable', true);
        element.setAttribute('twitch-tools-streamer-data', JSON.stringify(streamer));
        element.ondragstart ??= event => {
            let { currentTarget } = event;

            event.dataTransfer.setData('application/twitch-tools-streamer', currentTarget.getAttribute('twitch-tools-streamer-data'));
            event.dataTransfer.dropEffect = 'move';
        };
    }
);
// ...

3. Attempt to fold line 17 (it should be matched with line 22 but isn't)

Expected Behavior

1. The JavaScript syntax highlighter should distinguish between ?? and ? ...: ...
2. The highlighter should also allow the correct code-folding for ??

Actual Behavior

1. The syntax highlighter ignores ?? and treats it as ? ...: ...
2. Code-folding currently mismatches {} [] and () due to it thinking ?? ⇒ ? ...: ...

Reproduces how often:

100%

Versions

• Electron Version: 5.0.13
• Chrome Version: 73.0.3683.121
• Node Version: v12.0.0
• Operating System: Windows 10
• Last known working version: N/A

Additional Information

Screenshots

Incorrect pair being matched (line 17 → line 23)

Correct pair being matched (line 17 ← line 22)