[Analysis Server] Support for LSP semantic tokens

[ericdallo]

As discussed here and here there're some languages with support for the new semantic tokens protocol from LSP, which may come on LSP 3.16.
Here is the protocol definition.

Is it possible to add support for that?

Once implemented, we can start using on lsp-dart for Emacs and in the future, on VScode (c/c @DanTup).

[DanTup]

This is something on my radar - the current syntax highlighting in VS Code (powered by a TextMate grammar) has some issues so I'd like to move over to server-supplied highlighting (and the plan is for VS Code to switch over to LSP).

I don't expect to start looking at it until after the spec is finalised and supported by the vscode language server client though (to avoid reworking things if the spec evolves).

[DanTup]

Semantic tokens are available in the latest Dart/Flutter code (probably nightlies/master right now, though probably in dev soon too) - anything after 28523a5 should have them (though there have continued to be some improvements since then).

If you find any issues, please do file bugs here and CC me.

(@ericdallo I can't close issues here, so if you're happy with this please do that for me too :-))

[ericdallo]

Thank you @DanTup! I'll test it soon and let you know ;)