Bug Report

🔎 Search Terms

• lastIndexOf

🕗 Version & Regression Information

• This is a crash in tsserver.js
• This happens in 4.2.2, 4.2.3 and next (4.3.0-dev.20210305), but not version 4.1.5
• node version v14.15.4
• windows version 20H2

💻 Steps to reproduce

This happens consistently for me in the OmniSharp/omnisharp-vscode repository, when opening a typescript file with 4.2 installed.

1. git clone https://github.com/OmniSharp/omnisharp-vscode.git
2. cd omnisharp-vscode
3. npm install
4. npm install -g typescript@4.2.2
5. code .
6. Configure vscode to use the global ts server (for me this is "typescript.tsdk": "C:\\Users\\phil\\AppData\\Roaming\\npm\\node_modules\\typescript\\lib",)
7. Restart code
8. Open the TypeScript output to view errors

🙁 Actual behavior

The TypeScript language server crashes. Attached is a sample log:
tsserver.zip

🙂 Expected behavior

It to not crash.

Related Issues

There's a couple of related issues in vscode repo such as microsoft/vscode#115905