anchor.diff:            // If we didn't get a recent set of type checking results, we put in a request and wait for at most 'timeout' for a response
             match timeout with
             | Some timeout ->
  -            let! computation = Async.StartChild(x.ParseAndCheckFile(fileName, src, opts), timeout)
  +            let! computation = Async.StartChild(x.ParseAndCheckFile(fileName, src, opts, obs), timeout)
               try 
                 let! result = computation
                 return Some(result)
               with
               | :? System.TimeoutException -> return None
             | None ->
  -            let! result = x.ParseAndCheckFile(fileName, src, opts) 
  +            let! result = x.ParseAndCheckFile(fileName, src, opts, obs) 
               return Some(result) }
   
     /// Returns a TypeParsedResults if available, otherwise None
  
positive.code:     asyncMaybe {
        Debug.WriteLine("LanguageService: GetUsesOfSymbolAtLocationInFile: fileName={0}, line = {1}, col = {2}", fileName, line, col)
        let! colu, identIsland = Parsing.findLongIdents(col, lineStr) |> async.Return
        let! results = x.GetTypedParseResultWithTimeout(projectFilename, fileName, source, stale= AllowStaleResults.MatchingSource)
        let! symbolUse = results.GetSymbolAtLocation(line, colu, lineStr)
        let lastIdent = Seq.last identIsland
        let! refs = results.GetUsesOfSymbolInFile(symbolUse.Symbol) |> Async.map Some
  
negative.code: 
    /// Parses and checks the given file in the given project under the given configuration.
    ///Asynchronously returns the results of checking the file.
    member x.GetTypedParseResultWithTimeout(projectFilename, fileName:string, src, stale, ?timeout, ?obsoleteCheck) =
      let obs = defaultArg obsoleteCheck (IsResultObsolete(fun () -> false))
      async {
        let fileName = if Path.GetExtension fileName = ".sketchfs" then Path.ChangeExtension (fileName, ".fsx") else fileName
        let opts = x.GetCheckerOptions(fileName, projectFilename, src)
  