anchor.diff:      static member IterIntervals (action, charSet : CharSet) : unit =
           // Preconditions
           checkNonNull "charSet" charSet
  +        assert (CharDiet.dietInvariant charSet.Tree)
   
           let action = FSharpFunc<_,_,_>.Adapt action
           charSet.Tree |> AvlTree.Iter action.Invoke
  
positive.code:     static member ToList (charSet : CharSet) : char list =
          // Preconditions
          checkNonNull "charSet" charSet
  
          CharDiet.toList charSet.Tree
  
  
negative.code:     static member AddRange (lower, upper, charSet : CharSet) : CharSet =
          // Preconditions
          checkNonNull "charSet" charSet
          assert (CharDiet.dietInvariant charSet.Tree)
  
          // For compatibility with the F# range operator, we don't raise
          // an exception if lower > upper; that is considered an empty range,
  