anchor.diff:      /// Creates a new `CharSpan` that spans one character more than the given one.
       /// A `CharStream` must also be given to validate its length so that out-of-bounds errors are prevented.
       let extendSpanByOne (cs: CharStream) span =
  -        if span.IndexTo < cs.LengthSoFar then
  +        if span.IndexTo < cs.Source.LengthSoFar then
               {span with IndexTo = span.IndexTo + 1UL}
           else
               failwith "Trying to extend a character span by one character past these that were already read."
  
positive.code:     /// The default buffer size is 256 characters. If the specified size is not positive, the default is used.
      /// Also, the character stream must be disposed afterwards.
      let ofTextReaderEx bufferSize textReader =
          let buffer =
              if bufferSize > 0 then
                  bufferSize
              else
                  defaultBufferSize
              |> Array.zeroCreate
          {
              Reader = textReader
              Buffer = buffer
              BufferStartingIndex = 0UL
              NextReadIndex = 0UL
          } |> DynamicBlock |> create
  
      /// Creates a `CharStream` from a `TextReader`.
      /// It must be disposed afterwards.
  
negative.code:     /// Creates an arbitrary object out of the characters at the given `CharSpan`.
      /// After that call, the characters at and before the span might be freed from memory, so this function must not be used twice.
      let unpinSpanAndGenerate symbol (fPostProcess: CharStreamCallback<'symbol>) cs ({IndexFrom = idxStart; IndexTo = idxEnd} as span) =
          if cs.StartingIndex <= idxStart && cs.Source.LengthSoFar > idxEnd then
              cs.StartingIndex <- idxEnd + 1UL
              let length = idxEnd - idxStart + 1UL |> int
              let span = cs.Source.GetSpanForCharacters(idxStart, length)
              cs._LastUnpinnedSpanPosition <- cs.GetCurrentPosition()
              fPostProcess.Invoke(symbol, cs.LastUnpinnedSpanPosition, span)
          else
  