C# 代码着色程序错误

我试图写一个语法来解析一个语句，比如

b.a := 7;

我的语法如下所示

public class STGrammar : InterpretedLanguageGrammar
{
    public STGrammar() : base(caseSensitive: false)
    {
        LanguageFlags = LanguageFlags.CreateAst;

        # region Terminals
        Terminal n = new NumberLiteral("number");
        Terminal v = new IdentifierTerminal("variable");
        KeyTerm assignment = ToTerm(":=");
        KeyTerm left_paren = ToTerm("(");
        KeyTerm right_paren = ToTerm(")");
        KeyTerm terminate = ToTerm(";");
        KeyTerm left_sq = ToTerm("[");
        KeyTerm right_sq = ToTerm("]");
        KeyTerm dot = ToTerm(".");
        #endregion Terminals

        #region Nonterminals
        NonTerminal actionBlock = new NonTerminal("actionBlock", typeof(ActionBlock));
        NonTerminal assignmentExpr = new NonTerminal("assignmentExpr", typeof(AssignmentStNode));
        NonTerminal arrayOrStruct = new NonTerminal("arrayOrStruct", typeof(ArrayNode));
        NonTerminal arrayOrStructRHS = new NonTerminal("arrayOrStructRHS", typeof(AstNode));
        NonTerminal arrayOrStructRHSs = new NonTerminal("arrayOrStructRHSs");
        NonTerminal comparatorExp = new NonTerminal("comparatorExpression", typeof(ExpressionNode));
        #endregion Nonterminals

        #region BNFRules
        actionBlock.Rule =
            assignmentExpr + terminate
            | arrayOrStruct + terminate
            ;
        assignmentExpr.Rule =
            v + assignment + v
            | v + assignment + n
            | arrayOrStruct + assignment + v
            | v + assignment + arrayOrStruct
            | arrayOrStruct + assignment + arrayOrStruct
            | arrayOrStruct + assignment + n
            ;
        arrayOrStruct.Rule =
            v + arrayOrStructRHSs
            ;
        arrayOrStructRHS.Rule = 
            "." + v 
            | "[" + v + "]"
            ;
        arrayOrStructRHSs.Rule =
            MakePlusRule(arrayOrStructRHSs, arrayOrStructRHS)
            ;

        this.Root = actionBlock;

        #endregion BNFRules

        MarkPunctuation(",", ";", "[", "]", ")", "(", "..", ".");
        RegisterBracePair("(", ")");
    }
}

当我尝试解析时，它工作得很好

b := 7;

出现的错误是代码着色程序中的

致命错误。着色已被禁用。

即使我已注释掉

LanguageFlags = LanguageFlags.CreateAst;

错误仍然存在。 详细错误是

System.NullReferenceException was unhandled by user code
  Message=Object reference not set to an instance of an object.
  Source=Irony
  StackTrace:
       at Irony.Ast.AstBuilder.BuildAst(ParseTreeNode parseNode) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Ast\AstBuilder.cs:line 97
       at Irony.Ast.AstBuilder.BuildAst(ParseTreeNode parseNode) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Ast\AstBuilder.cs:line 86
       at Irony.Ast.AstBuilder.BuildAst(ParseTreeNode parseNode) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Ast\AstBuilder.cs:line 86
       at Irony.Ast.AstBuilder.BuildAst(ParseTreeNode parseNode) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Ast\AstBuilder.cs:line 86
       at Irony.Ast.AstBuilder.BuildAst(ParseTree parseTree) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Ast\AstBuilder.cs:line 38
       at Irony.Interpreter.InterpretedLanguageGrammar.BuildAst(LanguageData language, ParseTree parseTree) in C:\Sreeja\downloads\Irony_2013_03_10\Irony.Interpreter\InterpretedLanguageGrammar.cs:line 60
       at Irony.Parsing.Parser.Parse(String sourceText, String fileName) in C:\Sreeja\downloads\Irony_2013_03_10\Irony\Parsing\Parser\Parser.cs:line 88
       at Irony.GrammarExplorer.fmGrammarExplorer.ParseSample() in C:\Sreeja\downloads\Irony_2013_03_10\Irony.GrammarExplorer\fmGrammarExplorer.cs:line 348
       at Irony.GrammarExplorer.fmGrammarExplorer.btnParse_Click(Object sender, EventArgs e) in C:\Sreeja\downloads\Irony_2013_03_10\Irony.GrammarExplorer\fmGrammarExplorer.cs:line 507
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
  InnerException: 

有人能帮我解决这个错误吗？

---

我使用的是Irony_2013_03_10版本。

应该为所有非终端添加Ast节点类型，临时的除外。在每个Ast节点类中，重写Init（）和DoEvalute（）函数。详情见