Unable to parse the `#` symbol for private methods of a class

[iShibi]

Describe the bug

ℹ️ I've opened a related issue at acornjs as requested: acornjs/acorn-class-fields#17

Vitest throws error when testing an instance of a class that implements a private method. The error occurs because private method's name starts with the # symbol which it is unable to parse.

The project that I'm trying to add vitest to: twitterjs/twitter.js#96

Reproduction

https://stackblitz.com/edit/node-stkuzb

System Info

System:
  OS: Windows 10 10.0.19043
  CPU: (12) x64 AMD Ryzen 5 4600H with Radeon Graphics
  Memory: 2.09 GB / 7.36 GB
Binaries:
  Node: 16.9.0 - ~\AppData\Local\Volta\tools\image\node\16.9.0\node.EXE      
  Yarn: 1.22.11 - ~\AppData\Local\Volta\tools\image\yarn\1.22.11\bin\yarn.CMD
  npm: 7.24.2 - ~\AppData\Local\Volta\tools\image\npm\7.24.2\bin\npm.CMD     
Browsers:
  Edge: Spartan (44.19041.1266.0), Chromium (96.0.1054.62)
  Internet Explorer: 11.0.19041.1202
npmPackages:
  vitest: ^0.0.113 => 0.0.113

Used Package Manager

npm

Logs

FAIL  src/client/__tests__/Client.test.ts [ src/client/__tests__/Client.test.ts ]
Error: Parse failure: Unexpected token (60:8)
Contents of line 60:   async #fetchClientUser(username) {
 ❯ ssrTransform node_modules/vite/dist/node/chunks/dep-fcec4469.js:56614:15
 ❯ doTransform node_modules/vite/dist/node/chunks/dep-fcec4469.js:57940:48
 ❯ processTicksAndRejections ../../../node:internal/process/task_queues:96:5

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[iShibi]

from the above mentioned issue:

As of Acorn 8.2.0 private fields and private methods are supported in Acorn without the need to use this (or another) plugin, I recommend upgrading Acorn.

acornjs/acorn-class-fields#17 (comment)

[sheremet-va]

Should be fixed in 0.0.120