anchor.diff:      let parseInt = tryParse System.Int32.TryParse
       let parseTuple t mk (ds: D[]) : D =
           let k = Array.length ds
  -        let json =
  +        let json() =
               match ds |> Seq.filter (fun d -> d.ReadsJson()) |> Seq.length with
               | 0 -> false
               | 1 -> true
  
positive.code:             typeof<System.Enum>
                  .GetMethod("ToObject", [|typeof<System.Type>; uT|])
          let f = getD uT
          D.Make false <| fun p ->
              f.Decode p |> DecodeResult.map (fun x -> toObj.Invoke(null, [|t; x|]))
      elif t.IsArray then
          if t.GetArrayRank() > 1 then
  
negative.code:     }
      static member Make json decode =
          {
              ReadsJson = json
              Decode = decode
          }
  
  