show documentation in code completion

[liamdawson]

When Intellisense in VS Code suggests a method, it does not display the documentation for the method:

I would have expected it to show (at minimum):

Constructs a new Arc.

https://doc.rust-lang.org/std/sync/struct.Arc.html#method.new

I would love to contribute this feature, if someone can point me in the right direction.

[est31]

Its planned afaik, cc @steveklabnik

[Xanewok]

In general, an ad hoc way to implement this right now would probably be to, after retrieving completion data from Racer, map the CompletionItems and attach a documentation?: string to each CompletionItem.

There's a minor detail - you only have a hypothetical text completion and not an actual Span in the file/buffer (before applying the completion) that are pre-analyzed, and so for each completion you'd have to (I think) try to search_for_id and somehow guess (using some path heuristic?) a correct symbol Id (if there are multiple valid ones for each symbol name) and call docs for it.
This would be much simpler if you had a Span already, using id and maybe it's possible currently and I'm not seeing something.

Using this approach, this may or may not be noticeably more costly to fetch and prepare diagnostics, so it's also something to have in mind. However I do agree that'd be very, very handy to have!