F#: Editor features (intellisense etc) don't work after deleting ".vs"

[0x53A]

1. Create a new F# project Console App (.NET Core)

2. Let VS do its thing, after a few seconds everything works. Do a build for good measure.
   

3. Close VS and delete the .vs directory

4. reopen the solution: build works, but editor features don't
   

5. Restart VS one more time, after that, everything works again

[Pilchie]

@TIHan can you take a look at this?

[TIHan]

Yes, going to look at it now.

[Pilchie]

Leaving in 15.8 for investigations.

[TIHan]

I know what is happening now. F#'s language service is not being initialized unless a document has been opened. This means we miss out on all the workspace events that F#'s language service needs.

To be more specific, FSharpPackage doesn't get initialized until a F# document has been opened.

[TIHan]

I have a fix for this coming. It is a bug in the F# language service.

[davkean]

This issue was moved to dotnet/fsharp#5395