Question

I tried error reporting in following manner.

@members{
    public String getErrorMessage(RecognitionException e,String[] tokenNames)
    {
        List stack=getRuleInvocationStack(e,this.getClass().getName());
        String msg=null;
        if(e instanceof NoViableAltException){
            <some code>
        }
        else{
            msg=super.getErrorMessage(e,tokenNames);
        }
        String[] inputLines = e.input.toString().split("\r\n");
        String line = "";
        if(e.token.getCharPositionInLine()==0)
            line =  "at \"" + inputLines[e.token.getLine() - 2];
        else if(e.token.getCharPositionInLine()>0)
            line =  "at \"" + inputLines[e.token.getLine() - 1];
        return ": " + msg.split("at")[0] + line + "\" => [" + stack.get(stack.size() - 1) + "]";
    }

    public String getTokenErrorDisplay(Token t){
        return t.toString();
    }
}

And now errors are displayed as follows.

line 6:7 : missing CLOSSB at "int a[6;" => [var_declaration]
line 8:0 : missing SEMICOL at "int p" => [var_declaration]
line 8:5 : missing CLOSB at "get(2;" => [call]

I have 2 questions.

1) Is there a proper way to do the same thing I have done?

2) I want to replace CLOSSB, SEMICOL, CLOSB etc. with their real symbols. How can I do that using the map in .g file?

Thank you.

Answer 1

Bhathiya wrote:

*1) Is there a proper way to do the same thing I have done?

There is no single way to do this. Note that proper error-handling and reporting is tricky. Terence Parr spends a whole chapter on this in The Definitive ANTLR Reference (chapter 10). I recommend you get hold of a copy and read it.

Bhathiya wrote:

2) I want to replace CLOSSB, SEMICOL, CLOSB etc. with their real symbols. How can I do that using the map in .g file?

You can’t. For SEMICOL this may seem easy to do, but how would you get this information for a token like FOO:

FOO : (X | Y)+;

fragment X : '4'..'6';
fragment Y : 'a' | 'bc' | . ;