Broken shell script highlighting for array elements used as an array index

[foreignmeloman]

Version: 1.47.0-insider (user setup)
Commit: 376d9d9
Date: 2020-07-03T10:27:06.804Z
Electron: 7.3.2
Chrome: 78.0.3904.130
Node.js: 12.8.1
V8: 7.8.279.23-electron.0
OS: Windows_NT x64 10.0.16299

Steps to Reproduce:

Seems like vscode struggles with highlighting bash syntax correctly when array elements are used as an array index.
Example code:

echo ${a[${b[0]}]}

As you can see the last two symbols are not colored correctly:

This will only be visible with themes that have additional highlighting of some elements like the default Dark+.
I think that the closing square bracket in ${b[0]} is causing the issue, since when you remove the square brackets the highlighting goes back to normal:

Does this issue occur when all extensions are disabled?: Yes

[alexr00]

Thank you for filing this issue. It is a problem with the grammar we use for shell script syntax highlighting. Specifically, this tokenization is incorrect:

However, the repository we get the shell script grammar from is no longer maintaining the grammar. I'll leave this bug open so that if we adopt a new grammar it can be addressed.

[alexr00]

Linking and closing in favor of #77675, which tracks considering a new shellscript grammar.