anchor.diff:  
       /// Parses and post-processes a .NET `TextReader`. Its content is lazily read.
       let parseTextReader rf (textReader: TextReader) =
  +        nullCheck (nameof textReader) textReader
           use cs = new CharStream(textReader, true)
           parseChars rf cs
   
       /// Parses and post-processes a file at the given path.
       let parseFile rf path =
  +        nullCheck (nameof path) path
           use s = File.OpenText(path)
           parseTextReader rf s
   
  
positive.code: namespace Farkle
  
  open Farkle.Builder
  open Farkle.Grammar
  open Farkle.IO
  open Farkle.Parser
  
negative.code: 
      /// Parses and post-processes a string.
      let parseString rf (inputString: string) =
          nullCheck (nameof inputString) inputString
          use cs = new CharStream(inputString)
          parseChars rf cs
  
  