Hi Michael, Thanks for the reply. I agree that it was due to an error in my tree walker grammar (that I've now found and fixed), but I think it is pretty bad that ANTLR generates an internal error with no useful information, whenever I make a mistake in my grammar. It certainly doesn't make it easy to learn ANTLR and how to create tree parsers :-)
I was therefore hoping for Ter or someone else with access, to create an issue in the bug tracker, so it could be solved eventually. Regards Søren 2011/3/28 Michael Bedward <[email protected]> > Hi Søren, > > I see that error every so often and, so far al least, it has always > been due to an error in my tree walker grammar - specifically an > alternative that arises in the AST but that I forgot to consider in > the grammar. > > Michael > > On 28 March 2011 23:29, Søren Boisen <[email protected]> wrote: > > Greetings, > > I have a encountered a problem while trying to write a tree parser for my > > grammar. Sometimes when trying to walk the AST and the tree parser fails > to > > match some input, I get the following exception: > > > > can't look backwards more than one token in this stream > > org.antlr.runtime.misc.LookaheadStream.LB(LookaheadStream.java:159) > > org.antlr.runtime.misc.LookaheadStream.LT(LookaheadStream.java:120) > > > > > org.antlr.runtime.RecognitionException.extractInformationFromTreeNodeStream(RecognitionException.java:144) > > org.antlr.runtime.RecognitionException.(RecognitionException.java:111) > > > > > org.antlr.runtime.MismatchedTreeNodeException.(MismatchedTreeNodeException.java:42) > > > > > org.antlr.runtime.tree.TreeParser.recoverFromMismatchedToken(TreeParser.java:135) > > org.antlr.runtime.BaseRecognizer.match(BaseRecognizer.java:115) > > > > > com.brunata.ws.rest.odata.query.NearestTelegramQueryWalker.queryOp(NearestTelegramQueryWalker.java:243) > > > > > com.brunata.ws.rest.odata.query.NearestTelegramQueryWalker.stmt(NearestTelegramQueryWalker.java:128) > > > > I have looked through the FAQ, the issue tracker and Google, but I > couldn't > > find anything that looked related. > > > > From the stack trace it looks like an error in the > > extractInformationFromTreeNodeStream, since I guess it shouldn't expect > to > > always be able to look back more than one token in a stream. > > Is there a workaround for this? This is the code I use for creating > parsers > > and streams: > > > > String query = ...; // this is a parameter to the method > > Map<String, String> propertyFilters = ...; // this is a field on > the > > class > > > > ANTLRStringStream input = new ANTLRStringStream(query); > > QueryParserLexer lexer = new QueryParserLexer(input); > > > > CommonTokenStream tokens = new CommonTokenStream(lexer); > > QueryParserParser parser = new QueryParserParser(tokens); > > > > QueryParserParser.stmt_return result = tryParse(parser, query); > > ast = (CommonTree) result.getTree(); > > > > CommonTreeNodeStream nodes = new CommonTreeNodeStream(ast); > > nodes.setTokenStream(tokens); > > > > NearestTelegramQueryWalker walker = new > > NearestTelegramQueryWalker(nodes); > > propertyFilters = tryWalk(walker, query); > > > > Am I using the wrong kind of token/node streams or something? > > > > Regards, > > Søren Boisen > > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
