For classes we can see the inherited class in the tooltip  But for interfaces we cannot  [`IDocumentNavigationService` inherits `IWorkspaceService`](http://source.roslyn.io/#Microsoft.CodeAnalysis.Features/Navigation/IDocumentNavigationService.cs,9) This would be particularly useful for checking the service type when working with the Roslyn API and will synergize well with https://github.com/Microsoft/visualfsharp/pull/2574 and https://github.com/Microsoft/visualfsharp/pull/2603