anchor.diff:  
                   body.GetFreeVars ()
                   |> Seq.filter (fun freeVar -> not <| Set.contains freeVar parameterVars)
  -                |> Seq.sortBy (fun freeVar -> (if env.letrec = Some freeVar then 0 else 1), freeVar.Name)
  +                |> Seq.sortBy (fun freeVar -> freeVar.Name)
                   |> Seq.toList
   
  -            let isLetRec =
  -                match capturedVars with
  -                | first :: _ when Some first = env.letrec -> true
  -                | _ -> false
  +            let letRecVar = env.letrec
   
               let varsCount = vars.Length
               if varsCount <= 5 && capturedVars.Length <= 8 then
  
positive.code:     /// concert with later versions of LINQ.
      let rec ConvExpr (env:ConvEnv) (inp:Expr) = 
          match LetRecConvExpr env inp with
          | expr, None -> expr
          | _, Some _ -> failwith "Invalid logic"
      and LetRecConvExpr (env:ConvEnv) (inp:Expr) = 
         //printf "ConvExpr : %A\n" e;
          match inp with 
  
negative.code:         f7hole := f7
          f8hole := f8
          B.Invoke(f1,f2,f3,f4,f5,f6,f7,f8)
  *)
      type FuncFSharp<'state,'a> (f:Func<'state,'a>) =
          inherit FSharpFunc<unit, 'a>()
          [<Core.DefaultValue false>] val mutable State : 'state
  