wonder if this is why I'm seeing "evaluating local variables..." in VS while debugging. (#6595)

It seems a bit smoother when working with FSharp.sln fsi.exe but not tried under trace / profiling

Author: smoothdeveloper

src/fsharp/range.fs

@@ -252,11 +252,14 @@ type range(code1:int64, code2: int64) =
         try
             let endCol = r.EndColumn - 1
             let startCol = r.StartColumn - 1
-            File.ReadAllLines(r.FileName)
-            |> Seq.skip (r.StartLine - 1)
-            |> Seq.take (r.EndLine - r.StartLine + 1)
-            |> String.concat "\n"
-            |> fun s -> s.Substring(startCol + 1, s.LastIndexOf("\n", StringComparison.Ordinal) + 1 - startCol + endCol)
+            if FileSystem.IsInvalidPathShim r.FileName then "path invalid: " + r.FileName
+            elif not (FileSystem.SafeExists r.FileName) then "non existing file: " + r.FileName
+            else
+              File.ReadAllLines(r.FileName)
+              |> Seq.skip (r.StartLine - 1)
+              |> Seq.take (r.EndLine - r.StartLine + 1)
+              |> String.concat "\n"
+              |> fun s -> s.Substring(startCol + 1, s.LastIndexOf("\n", StringComparison.Ordinal) + 1 - startCol + endCol)
         with e ->
             e.ToString()        
 #endif