Implement hint dynamic unfolding

[SomeoneToIgnore]

Depending on the user settings, rust-analyzer server can fold too long hints, i.e. HashMap<String, Vec<...>>.

Now, when the VSCode client hints consist of ranges and support dynamic actions, we can make those folded hints dynamic and unfold them on click, similarly how Intellij does this now.

[roife]

I find this feature very interesting! I would like to take the time to explore its implementation.

Currently, ctrl + click the inlay hint label triggers the corresponding commands. My suggestion is that when the type is too long, it should display as Option<…>. ctrl + click the … would then expand it to Option<i32> ↩, and ctrl + click the ↩ would collapse it back.

[roife]

The main challenge is that the server cannot control when the client refreshes the inlay hints. As a result, we may need to add a state to server to track the expanded status of the hints, which could complicate the server.

[Veykril]

This sounds more like logic that the client should contain, not the server. So I don't think this is workable from our side

[roife]

It's indeed more suitable for the client to implement. Currently, VS Code truncates hints that exceed a certain length. A better solution would be to selectively collapse deeper hints based on their labels. However, the client needs to understand the structure of these labels to do this...

[Veykril]

The client has that information, the lsp encodes inlay hint parts already. To me this really sounds more like a feature request for editors (that is VSCode, Zed, etc)

[SomeoneToIgnore]

I actually agree now with the "it should be done in the editor" sentiment in the current days, hence closing.

[roife]

How about adding a tooltip to ... that displays the collapsed part or the entire type? Currently, the only way to view hidden parts is to select the expression and hover over it.

[Veykril]

That we can do on the server yes