anchor.diff:           override cc'.DoWork (wr) =
             let mutable nth = 0
             while xJs.MoveNext () do
  +            let xJ = xJs.Current
               cc'.Lock.ExitAndEnter (&wr, cc')
  -            let xJ = xJs.Current
               cc'.ysK.Value.Add Unchecked.defaultof<_>
               Worker.PushNew (&wr, {new Cont_State<_, _, _> (xJ, Util.dec &nth) with
  -             override xK'.DoHandle (wr, e) = cc'.OutsideDoHandle (&wr, e)
  +             override xK'.DoHandle (wr, e) = ConCollect<'x>.OutsideDoHandle (cc', &wr, e)
                override xK'.DoCont (wr, x) =
                 xK'.Value <- x
                 xK'.State2 <- ~~~ xK'.State2
  
positive.code:                    cc'.Lock.Enter (&wr, xK')
                   else
                     cc'.ysK.Value.[i] <- xK'.Value
                     cc'.Inc (&wr)
                 | xJ ->
                   xK'.State1 <- null
                   xJ.DoJob (&wr, xK')})
            cc'.Inc (&wr)}
         wr.Handler <- cc'
         cc'.Lock.Enter (&wr, cc')}
  
  
negative.code:      ConIgnore.AddExn (self, e)
       ConIgnore.Done (self, &wr)
  
    let conIgnore (xJs: seq<Job<'x>>) =
      {new Job<unit> () with
        override uJ.DoJob (wr, uK) =
  