anchor.diff:          |> InUseDetection.GetProcessesUsingFiles
           |> List.ofSeq<Process>
           |> fun ps -> match ps with
  -                     | [] -> nativeint 0
  -                     | p :: _ -> p.MainWindowHandle
  +                     | [] -> Failure "Can't find the process"
  +                     | p :: _ -> Success p.MainWindowHandle
   
   
       let internal SelectHandle getProcHandle findLockHandle (input: Input) log = 
  
positive.code: 
  module PopOpen =
  
      type Result<'nativeint> =
          | Success
          | Failure
  
      
      type Input = { File: string; Prc: Process }
  
negative.code: 
      let internal FindProcessHandle (input : Input) =
          try
              Success input.Prc.MainWindowHandle
          with
              | :? System.InvalidOperationException -> Failure "InvalidOperationException"
              | :? System.NullReferenceException -> Failure "NullReferenceException"
  
  
      let internal FindLockHandle (input: Input) =
  