Upcoming changes in "when clause"s

[ulugbekna]

Hello everyone 👋🙂

The next VS Code release is planned to include a new parser of when clauses. The new parser will come with new features, more precise but stricter parsing rules (so possible breakages), and a linter to see incorrect when clauses right away in extension's manifest file (i.e., package.json). I invite all extension authors to have a look at the upcoming changes described in this issue, subscribe to the issue in case there're any updates, and leave feedback if you have any.

P.S. For this feature, I had to look through hundreds of "when clauses" in existing extensions, and I would like to thank all extension authors for the awesome work and lots of effort put into providing best experience for their users! ❤️