How to collect errors during run time given by a parser in Antlr4

Question

I have upgraded from Antlr 3 to Antlr 4. I was using this code to catch exceptions using this code. But this is not working for Antlr 4.

partial class XParser
{
    public override void ReportError(RecognitionException e)
    {
        base.ReportError(e);
        Console.WriteLine("Error in Parser at line " + ":" + e.OffendingToken.Column + e.OffendingToken.Line + e.Message);
    }
}

This is the error that appears

'Parser.ReportError(Antlr4.Runtime.RecognitionException)': no suitable method found to override

In Antlr 4 what is the expected way of accumulating errors that occurs in the input stream. I was unable to find a way to achieve this on the net. Please provide me some guidelines.

EDIT:

I have implemented the XParser as below

partial class XParser : IAntlrErrorListener<IToken>
{
    public void SyntaxError(IRecognizer recognizer, IToken offendingSymbol, int line, int charPositionInLine, string msg, RecognitionException e)
    {
        Console.WriteLine("Error in parser at line " + ":" + e.OffendingToken.Column + e.OffendingToken.Line + e.Message);
    }
}

As you said I can extend this parser class using any of the mentioned classes. But I was unable to register this listener, in the main program I am confused with passing argument as the listener. Please help me with the registering.

As I can see these classes has the capability of producing more meaningful error messages don't they?

Customable

Answer 1

You need to implement IAntlrErrorListener<IToken>. If all you want to is report errors like you have above, then you should focus on the SyntaxError method. Several base classes are available if you want to extend one.

• ConsoleErrorListener
• BaseErrorListener
• DiagnosticErrorListener

The error listener is attached to the parser instance by calling parser.AddErrorListener(listener).

Edit: You need to create a new class which implements the error listener interface. You then attach the listener to the parser. The parser itself will not implement the error listener interface.

Madera

Please take a look at my edit. I have some confusion and clarification. Thanks for the big help through out the work. Appreciate it a lot. – Customable

@290Z28 Thanks that works. Why can't I do the same thing to Lexer. I tried to imitate what I did for the parser by creating another class and implementing from IAntlrErrorListener<IToken> . lexer instance has AddErrorListener a method. – Customable

confused with the name :) – Customable