c# - 学步车可以停下来吗？

Question

我有一个 ParseTree 监听器实现，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;
    }
}

有没有办法告诉树行者停止行走？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

我希望树遍历器在进入 Public Sub DoSomething() 后立即停止遍历解析树，因为我对下面的任何内容都不感兴趣。目前我正在遍历整个解析树，只是不对过程范围内的任何内容进行任何处理。

有没有办法从解析树监听器实现中告诉 walker 停止遍历树？

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 ParseTreeWalker 的新类，并提供您自己的 walk 实现它了解您需要的取消概念。从 current implementation of walk 开始是有意义的并对其进行修改以满足您的需求。