[antlr-interest] How can I find the line number and column for asemantic error

[Sam Harwell]

Add an ErrorHandler member to your parser, with an AddError method. Call
it from both your override of ReportError and wherever you want to add
your own semantic error. I have a whole bunch of helper methods like the
following as well. Please note that this code is not plug-and-play;
you'll have to implement your own ErrorHandler class and TextSpan is
probably not a type in your program, etc. I only mean this as a
human-readable example of a method that's worked for me. :)

 

public override void ReportError( RecognitionException e )

{

    if ( state.backtracking == 0 )

    {

        string message = GetErrorMessage( e, GetTokenNames() );

        TextSpan span = new TextSpan()

        {

            iStartLine = e.line - 1,

            iStartIndex = e.charPositionInLine,

            iEndLine = e.line - 1,

            iEndIndex = e.charPositionInLine + 1

        };

 

        if ( ( e.token == null || e.token.Type == 0 )

            && e.node is CommonErrorNode

            && ( (CommonErrorNode)e.node ).trappedException != null )

        {

            e.token = ( (CommonErrorNode)e.node
).trappedException.token;

        }

 

        if ( e.token != null )

        {

            if ( e.token.Type != (int)CharStreamConstants.Eof )

                span = e.token.ToTextSpan();

            else

                span = TokenStream.LT( -1 ).ToTextSpan();

        }

 

        string tokentext = e.token.Text ?? string.Empty;

 

        if ( ErrorHandler != null )

            ErrorHandler.AddError( "Parser: " + message, span.iStartLine
+ 1, span.iStartIndex, tokentext.Length, Severity.Error, true );

    }

 

    base.ReportError( e );

}

 

public void AddError( string message, CommonTree tree )

{

    if ( tree == null )

        return;

 

    AddError( message, (CommonToken)tree.Token );

}

public void AddError( string message, CommonTree tree, Severity severity
)

{

    if ( tree == null )

        return;

 

    AddError( message, (CommonToken)tree.Token, severity );

}

public void AddError( string message, CommonToken token )

{

    if ( token == null )

        return;

 

    AddError( message, token, Severity.Error );

}

public void AddError( string message, CommonToken token, Severity
severity )

{

    if ( string.IsNullOrEmpty( message ) || token == null ||
ErrorHandler == null )

        return;

 

    int line = token.Line;

    int col = token.CharPositionInLine;

    int length = token.StopIndex - token.StartIndex + 1;

    // these errors aren't forcing the parser into recovery mode so they

    // shouldn't have the same devastating performance impact

    bool canCancel = false;

 

    ErrorHandler.AddError( message, line, col, length, severity,
canCancel );

}

 

public void AddWarning( string message, CommonTree tree )

{

    AddError( message, tree, Severity.Warning );

}

public void AddWarning( string message, CommonToken token )

{

    AddError( message, token, Severity.Warning );

}

 

 

Sam Harwell

 

-----Original Message-----
From: antlr-interest-bounces at antlr.org
[mailto:antlr-interest-bounces at antlr.org] On Behalf Of dhjdhj
Sent: Friday, April 10, 2009 11:16 AM
To: antlr-interest at antlr.org
Subject: [antlr-interest] How can I find the line number and column for
asemantic error

 

I understand that if I get a RecognitionException, I can extract the  

line and column from the exeception.

 

However, suppose I'm inside a rule and I decide that I have a semantic  

error (i.e, variable types aren't compatible  or something). At that  

point I want to generate a Semantic Error that will be caught at the  

top level but I still need to know (at least) what line the semantic  

error occurred. I tried to get that info out of the lexer but it  

always returns the last line of the source code so that doesn't help.

 

I must be missing something non-obvious (to me) and would appreciate  

suggestions.

 

Thanks,

David Jameson

 

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