步行者可以停下来吗？

Question

我有一个ParseTree侦听器实现,我用它来获取标准VBA模块中的全局范围声明:

public class DeclarationSectionListener : DeclarationListener
{
    private bool _insideProcedure;

    public override void EnterVariableStmt(VisualBasic6Parser.VariableStmtContext context)
    {
        var visibility = context.visibility();
        if (!_insideProcedure && visibility == null 
            || visibility.GetText() == Tokens.Public
            || visibility.GetText() == Tokens.Global)
        {
            base.EnterVariableStmt(context);
        }
    }

    public override void EnterConstStmt(VisualBasic6Parser.ConstStmtContext context)
    {
        var visibility = context.visibility();
        if (!_insideProcedure && visibility == null
            || visibility.GetText() == Tokens.Public
            || visibility.GetText() == Tokens.Global)
        {
            base.EnterConstStmt(context);
        }
    }

    public override void EnterArg(VisualBasic6Parser.ArgContext context)
    {
        return;
    }

    public override void EnterSubStmt(VisualBasic6Parser.SubStmtContext context)
    {
        _insideProcedure = true;
    }

    public override void EnterFunctionStmt(VisualBasic6Parser.FunctionStmtContext context)
    {
        _insideProcedure = true;
    }

    public override void EnterPropertyGetStmt(VisualBasic6Parser.PropertyGetStmtContext context)
    {
        _insideProcedure = true;
    }

    public override void EnterPropertyLetStmt(VisualBasic6Parser.PropertyLetStmtContext context)
    {
        _insideProcedure = true;
    }

    public override void ExitPropertySetStmt(VisualBasic6Parser.PropertySetStmtContext context)
    {
        _insideProcedure = true;
    }
}

有办法告诉树木步行者不要走路吗？假设我有一个像这样的VBA模块:

Public Const foo = 123
Public bar As String

Public Sub DoSomething()
    ' some code
End Sub

' ...
' 10K more lines of code
' ...

Private Function GetSomething() As String
     ' some code 
End Function

我希望树步行者一进入就停止走在解析树上Public Sub DoSomething(),因为我对这下面的任何东西都不感兴趣.目前我正在遍历整个解析树,只是在程序范围内没有做任何事情.

从解析树监听器实现中有没有办法告诉walker停止走树？

Answer 1

是的,您可以执行以下任一操作:

1. 抛出异常,例如CancellationException
2. 创建一个扩展的新类ParseTreeWalker,并提供您自己的实现walk,了解您需要的取消概念.从当前的实现walk开始并对其进行修改以满足您的需求是有意义的.