anchor.diff:                  then
                       let varName = tok |> tokToSourceString
   
  -                    if not <| List.exists (fun t -> t = varName) !defVars //it's error
  +                    //Is it error?
  +                    if not <| List.exists (fun t -> t = varName) !defVars
                       then
                           let tokData = parserSource.tokenData tok
  -                        //if it's new error
  +                        //is it new error?
                           if not <| List.exists (fun t -> parserSource.tokenData t = tokData) !errorList     
                           then errorList := tok :: !errorList 
   
  
positive.code:                                     processBlock child
  
                              else
                                  blockToVars.Add(child, defVars)
                                  processBlock child
                      )
  
  
negative.code:         let updateVertices() = 
              bStartVertex := !bEndVertex
              incr bEndVertex
  
          let restoreContext() = 
              let oldType, oldTokens, oldWasElse = stack.Pop()
  