anchor.diff:      inherit IMod<IBuffer>
       abstract member Clear : unit -> unit
       abstract member Capacity : int
  +    abstract member Set : nativeint * IntPtr * nativeint -> unit
       abstract member Set : Range1l * byte[] -> unit
       abstract member Add : Range1l * BufferView -> IDisposable
       abstract member Add : int * IMod -> IDisposable
  
positive.code: 
              x.Store.Upload(byteOffset, src, byteCount)
  
          member x.Set(range : Range1l, value : byte[]) =
              let count = range.Size + 1L
              let e = nativeint(range.Min + count) * asize
  
negative.code:             member x.Clear() = x.Clear()
              member x.Add(range : Range1l, view : BufferView) = x.Add(range, view)
              member x.Add(index : int, data : IMod) = x.Add(index, data)
              member x.Set(byteOffset : nativeint, src : IntPtr, byteCount : nativeint) = x.Set(byteOffset, src, byteCount)
              member x.Set(range : Range1l, value : byte[]) = x.Set(range, value)
              member x.Capacity = x.Capacity |> int
              member x.ElementType = typeof<'a>
  