[antlr-interest] Think I found a bug.

[James Reid]

Hi all,

  I think I found a bug but I want to be sure.  I have a parser grammar that
I run two passes on.  Here are short versions of the rules.



firstpass
  :  (collect_matches
  |  collect_labels
  |  .)*
  ;


script
  :  header? matches* EOF
  ;


When I run the code I use a CommonTokenStream and do the following

CommonTokenStream tokens = new CommonTokenStream(lex);
MyParser parser = new MyParser(tokens);

parser.firstpass();

tokens.reset();

parser.script();


The problem comes when I do the tokens.reset().  If the very first token is
a comment (i.e. on the hidden channel) it is returned in parser.script() and
throws a NoViableAlternativeException because nothing in my grammar is
expecting a comment.  To get around this I do the following...

           //Reset the tokens back to the begining
            tokens.reset();

            //For some reason after the tokens have been buffered up if a
hidden
            //token is the first token it is returned instead getting the
            //first non-hidden token.  This little hack works around that.
            if (tokens.LT(1).getChannel() == Token.HIDDEN_CHANNEL){
                tokens.consume();
            }

            //now we can build the AST
            r=parser.script();

If I consume the hidden token then the token stream points at the next
on-channel token like it is supposed to do.  Is this a bug or am I doing
things wrong?

Thanks,
James

PS:  This is with Antlr 3.3