anchor.diff:  
   module Yard.Generators.Common.AST
   open System
  +open System.IO
   open System.Collections.Generic
   open Yard.Generators.Common.DataStructures
   open Yard.Generators.Common.AstNode
  
positive.code: type private DotNodeType = Prod | AstNodeType
  
  type ErrorNode<'TokenType> = 
      val errorOn : Option<'TokenType>     // token on which error occurs
      val production : int  // now it doesn't work. Production number where error occured
      val expected : array<string>  // parser was expecting one of the these tokens
  
      val mutable tokens : array<'TokenType>  //skipped tokens during error recovery
      val recTokens : array<string> // parser was look for one of these tokens during recovery
  
      new (errOn, prod, exp, (*skip,*) recToks) = 
          {
  
negative.code:         let nodeToNumber = new System.Collections.Hashtable({new Collections.IEqualityComparer with
                                                                      override this.Equals (x1, x2) = Object.ReferenceEquals (x1, x2)
                                                                      override this.GetHashCode x = x.GetHashCode()})
          use out = new StreamWriter (path : string)
          out.WriteLine("digraph AST {")
  
          let createNode num isAmbiguous nodeType (str : string) =
  