Exemplo n.º 1
0
        /** Remove any lexer rules from a COMBINED; already passed to lexer */
        protected void TrimGrammar()
        {
            if (grammar.type != GrammarType.Combined)
            {
                return;
            }
            // form is (header ... ) ( grammar ID (scope ...) ... ( rule ... ) ( rule ... ) ... )
            GrammarAST p = root;

            // find the grammar spec
            while (!p.Text.Equals("grammar"))
            {
                p = (GrammarAST)p.Parent.GetChild(p.ChildIndex + 1);
            }
            for (int i = 0; i < p.ChildCount; i++)
            {
                if (p.GetChild(i).Type != RULE)
                {
                    continue;
                }

                string ruleName = p.GetChild(i).GetChild(0).Text;
                //Console.Out.WriteLine( "rule " + ruleName + " prev=" + prev.getText() );
                if (Rule.GetRuleType(ruleName) == RuleType.Lexer)
                {
                    // remove lexer rule
                    p.DeleteChild(i);
                    i--;
                }
            }
            //Console.Out.WriteLine( "root after removal is: " + root.ToStringList() );
        }
Exemplo n.º 2
0
        protected virtual GrammarAST ExpandOptionalQuantifiersForAlt(GrammarAST alt)
        {
            if (alt.ChildCount == 0)
            {
                return(null);
            }

            if (alt.GetChild(0).Type == ANTLRParser.OPTIONAL)
            {
                GrammarAST root = (GrammarAST)adaptor.Nil();

                GrammarAST alt2 = alt.DupTree();
                alt2.DeleteChild(0);
                if (alt2.ChildCount == 0)
                {
                    adaptor.AddChild(alt2, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                }

                alt.SetChild(0, alt.GetChild(0).GetChild(0));
                if (alt.GetChild(0).Type == ANTLRParser.BLOCK && alt.GetChild(0).ChildCount == 1 && alt.GetChild(0).GetChild(0).Type == ANTLRParser.ALT)
                {
                    GrammarAST list = (GrammarAST)adaptor.Nil();
                    foreach (object tree in ((GrammarAST)alt.GetChild(0).GetChild(0)).Children)
                    {
                        adaptor.AddChild(list, tree);
                    }

                    adaptor.ReplaceChildren(alt, 0, 0, list);
                }

                adaptor.AddChild(root, alt);
                adaptor.AddChild(root, alt2);
                return(root);
            }
            else if (alt.GetChild(0).Type == ANTLRParser.CLOSURE)
            {
                GrammarAST root = (GrammarAST)adaptor.Nil();

                GrammarAST alt2 = alt.DupTree();
                alt2.DeleteChild(0);
                if (alt2.ChildCount == 0)
                {
                    adaptor.AddChild(alt2, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                }

                PlusBlockAST plusBlockAST = new PlusBlockAST(ANTLRParser.POSITIVE_CLOSURE, adaptor.CreateToken(ANTLRParser.POSITIVE_CLOSURE, "+"), null);
                for (int i = 0; i < alt.GetChild(0).ChildCount; i++)
                {
                    plusBlockAST.AddChild(alt.GetChild(0).GetChild(i));
                }

                alt.SetChild(0, plusBlockAST);

                adaptor.AddChild(root, alt);
                adaptor.AddChild(root, alt2);
                return(root);
            }

            return(alt);
        }
Exemplo n.º 3
0
        // TODO: this strips the tree properly, but since text()
        // uses the start of stop token index and gets text from that
        // ineffectively ignores this routine.
        public virtual GrammarAST StripLeftRecursion(GrammarAST altAST)
        {
            GrammarAST lrlabel            = null;
            GrammarAST first              = (GrammarAST)altAST.GetChild(0);
            int        leftRecurRuleIndex = 0;

            if (first.Type == ELEMENT_OPTIONS)
            {
                first = (GrammarAST)altAST.GetChild(1);
                leftRecurRuleIndex = 1;
            }

            ITree rref = first.GetChild(1); // if label=rule

            if ((first.Type == RULE_REF && first.Text.Equals(ruleName)) ||
                (rref != null && rref.Type == RULE_REF && rref.Text.Equals(ruleName)))
            {
                if (first.Type == ASSIGN || first.Type == PLUS_ASSIGN)
                {
                    lrlabel = (GrammarAST)first.GetChild(0);
                }
                // remove rule ref (first child unless options present)
                altAST.DeleteChild(leftRecurRuleIndex);
                // reset index so it prints properly (sets token range of
                // ALT to start to right of left recur rule we deleted)
                GrammarAST newFirstChild = (GrammarAST)altAST.GetChild(leftRecurRuleIndex);
                altAST.TokenStartIndex = newFirstChild.TokenStartIndex;
            }

            return(lrlabel);
        }
Exemplo n.º 4
0
        protected virtual GrammarAST TranslateLeftFactoredElement(GrammarAST element, string factoredRule, bool variant, DecisionFactorMode mode, bool includeFactoredElement)
        {
            if (mode == DecisionFactorMode.PARTIAL_UNFACTORED && includeFactoredElement)
            {
                throw new ArgumentException("Cannot include the factored element in unfactored alternatives.");
            }

            if (mode == DecisionFactorMode.COMBINED_FACTOR)
            {
                throw new InvalidOperationException("Cannot return a combined answer.");
            }

            Debug.Assert(!mode.IncludeFactoredAlts() || !mode.IncludeUnfactoredAlts());

            switch (element.Type)
            {
            case ANTLRParser.ASSIGN:
            case ANTLRParser.PLUS_ASSIGN:
            {
                /* label=a
                 *
                 * ==>
                 *
                 * factoredElement label=a_factored
                 */

                GrammarAST translatedChildElement = TranslateLeftFactoredElement((GrammarAST)element.GetChild(1), factoredRule, variant, mode, includeFactoredElement);
                if (translatedChildElement == null)
                {
                    return(null);
                }

                RuleAST ruleAST = (RuleAST)element.GetAncestor(ANTLRParser.RULE);

#if false
                LOGGER.log(Level.WARNING, "Could not left factor ''{0}'' out of decision in rule ''{1}'': labeled rule references are not yet supported.",
                           new object[] { factoredRule, ruleAST.GetChild(0).Text });
#endif

                return(null);
                //if (!translatedChildElement.IsNil)
                //{
                //    GrammarAST root = (GrammarAST)adaptor.Nil();
                //    object factoredElement = translatedChildElement;
                //    if (outerRule)
                //    {
                //        adaptor.AddChild(root, factoredElement);
                //    }

                //    string action = string.Format("_localctx.{0} = (ContextType)_localctx.getParent().getChild(_localctx.getParent().getChildCount() - 1);", element.GetChild(0).Text);
                //    adaptor.AddChild(root, new ActionAST(adaptor.CreateToken(ANTLRParser.ACTION, action)));
                //    return root;
                //}
                //else
                //{
                //    GrammarAST root = (GrammarAST)adaptor.Nil();
                //    object factoredElement = adaptor.DeleteChild(translatedChildElement, 0);
                //    if (outerRule)
                //    {
                //        adaptor.AddChild(root, factoredElement);
                //    }

                //    adaptor.AddChild(root, element);
                //    adaptor.ReplaceChildren(element, 1, 1, translatedChildElement);
                //    return root;
                //}
            }

            case ANTLRParser.RULE_REF:
            {
                if (factoredRule.Equals(element.Token.Text))
                {
                    if (!mode.IncludeFactoredAlts())
                    {
                        return(null);
                    }

                    if (includeFactoredElement)
                    {
                        // this element is already left factored
                        return(element);
                    }

                    GrammarAST root1 = (GrammarAST)adaptor.Nil();
                    root1.AddChild((ITree)adaptor.Create(TokenConstants.Epsilon, "EPSILON"));
                    root1.DeleteChild(0);
                    return(root1);
                }

                Rule targetRule;
                if (!_rules.TryGetValue(element.Token.Text, out targetRule))
                {
                    return(null);
                }

                RuleVariants ruleVariants = CreateLeftFactoredRuleVariant(targetRule, factoredRule);
                switch (ruleVariants)
                {
                case RuleVariants.NONE:
                    if (!mode.IncludeUnfactoredAlts())
                    {
                        return(null);
                    }

                    // just call the original rule (leave the element unchanged)
                    return(element);

                case RuleVariants.FULLY_FACTORED:
                    if (!mode.IncludeFactoredAlts())
                    {
                        return(null);
                    }

                    break;

                case RuleVariants.PARTIALLY_FACTORED:
                    break;

                default:
                    throw new InvalidOperationException();
                }

                string marker = mode.IncludeFactoredAlts() ? ATNSimulator.RuleLfVariantMarker : ATNSimulator.RuleNolfVariantMarker;
                element.SetText(element.Text + marker + factoredRule);

                GrammarAST root = (GrammarAST)adaptor.Nil();

                if (includeFactoredElement)
                {
                    Debug.Assert(mode.IncludeFactoredAlts());
                    RuleRefAST factoredRuleRef = new RuleRefAST(adaptor.CreateToken(ANTLRParser.RULE_REF, factoredRule));
                    factoredRuleRef.SetOption(SUPPRESS_ACCESSOR, (GrammarAST)adaptor.Create(ANTLRParser.ID, "true"));
                    Rule factoredRuleDef = _rules[factoredRule];
                    if (factoredRuleDef is LeftRecursiveRule)
                    {
                        factoredRuleRef.SetOption(LeftRecursiveRuleTransformer.PRECEDENCE_OPTION_NAME, (GrammarAST)adaptor.Create(ANTLRParser.INT, "0"));
                    }

                    if (factoredRuleDef.args != null && factoredRuleDef.args.Size() > 0)
                    {
                        throw new NotImplementedException("Cannot left-factor rules with arguments yet.");
                    }

                    adaptor.AddChild(root, factoredRuleRef);
                }

                adaptor.AddChild(root, element);

                return(root);
            }

            case ANTLRParser.BLOCK:
            {
                GrammarAST cloned = element.DupTree();
                if (!TranslateLeftFactoredDecision(cloned, factoredRule, variant, mode, includeFactoredElement))
                {
                    return(null);
                }

                if (cloned.ChildCount != 1)
                {
                    return(null);
                }

                GrammarAST root = (GrammarAST)adaptor.Nil();
                for (int i = 0; i < cloned.GetChild(0).ChildCount; i++)
                {
                    adaptor.AddChild(root, cloned.GetChild(0).GetChild(i));
                }

                return(root);
            }

            case ANTLRParser.POSITIVE_CLOSURE:
            {
                /* a+
                 *
                 * =>
                 *
                 * factoredElement a_factored a*
                 */

                GrammarAST originalChildElement = (GrammarAST)element.GetChild(0);
                GrammarAST translatedElement    = TranslateLeftFactoredElement(originalChildElement.DupTree(), factoredRule, variant, mode, includeFactoredElement);
                if (translatedElement == null)
                {
                    return(null);
                }

                GrammarAST closure = new StarBlockAST(ANTLRParser.CLOSURE, adaptor.CreateToken(ANTLRParser.CLOSURE, "CLOSURE"), null);
                adaptor.AddChild(closure, originalChildElement);

                GrammarAST root = (GrammarAST)adaptor.Nil();
                if (mode.IncludeFactoredAlts())
                {
                    if (includeFactoredElement)
                    {
                        object factoredElement = adaptor.DeleteChild(translatedElement, 0);
                        adaptor.AddChild(root, factoredElement);
                    }
                }
                adaptor.AddChild(root, translatedElement);
                adaptor.AddChild(root, closure);
                return(root);
            }

            case ANTLRParser.CLOSURE:
            case ANTLRParser.OPTIONAL:
                // not yet supported
                if (mode.IncludeUnfactoredAlts())
                {
                    return(element);
                }

                return(null);

            case ANTLRParser.DOT:
                // ref to imported grammar, not yet supported
                if (mode.IncludeUnfactoredAlts())
                {
                    return(element);
                }

                return(null);

            case ANTLRParser.ACTION:
            case ANTLRParser.SEMPRED:
                if (mode.IncludeUnfactoredAlts())
                {
                    return(element);
                }

                return(null);

            case ANTLRParser.WILDCARD:
            case ANTLRParser.STRING_LITERAL:
            case ANTLRParser.TOKEN_REF:
            case ANTLRParser.NOT:
                // terminals
                if (mode.IncludeUnfactoredAlts())
                {
                    return(element);
                }

                return(null);

            case ANTLRParser.EPSILON:
                // empty tree
                if (mode.IncludeUnfactoredAlts())
                {
                    return(element);
                }

                return(null);

            default:
                // unknown
                return(null);
            }
        }
Exemplo n.º 5
0
        protected virtual bool TranslateLeftFactoredDecision(GrammarAST block, string factoredRule, bool variant, DecisionFactorMode mode, bool includeFactoredElement)
        {
            if (mode == DecisionFactorMode.PARTIAL_UNFACTORED && includeFactoredElement)
            {
                throw new ArgumentException("Cannot include the factored element in unfactored alternatives.");
            }
            else if (mode == DecisionFactorMode.COMBINED_FACTOR && !includeFactoredElement)
            {
                throw new ArgumentException("Cannot return a combined answer without the factored element.");
            }

            if (!ExpandOptionalQuantifiersForBlock(block, variant))
            {
                return(false);
            }

            IList <GrammarAST> alternatives = block.GetAllChildrenWithType(ANTLRParser.ALT);

            GrammarAST[] factoredAlternatives   = new GrammarAST[alternatives.Count];
            GrammarAST[] unfactoredAlternatives = new GrammarAST[alternatives.Count];
            IntervalSet  factoredIntervals      = new IntervalSet();
            IntervalSet  unfactoredIntervals    = new IntervalSet();

            for (int i = 0; i < alternatives.Count; i++)
            {
                GrammarAST alternative = alternatives[i];
                if (mode.IncludeUnfactoredAlts())
                {
                    GrammarAST unfactoredAlt = TranslateLeftFactoredAlternative(alternative.DupTree(), factoredRule, variant, DecisionFactorMode.PARTIAL_UNFACTORED, false);
                    unfactoredAlternatives[i] = unfactoredAlt;
                    if (unfactoredAlt != null)
                    {
                        unfactoredIntervals.Add(i);
                    }
                }

                if (mode.IncludeFactoredAlts())
                {
                    GrammarAST factoredAlt = TranslateLeftFactoredAlternative(alternative, factoredRule, variant, mode == DecisionFactorMode.COMBINED_FACTOR ? DecisionFactorMode.PARTIAL_FACTORED : DecisionFactorMode.FULL_FACTOR, includeFactoredElement);
                    factoredAlternatives[i] = factoredAlt;
                    if (factoredAlt != null)
                    {
                        factoredIntervals.Add(alternative.ChildIndex);
                    }
                }
            }

            if (factoredIntervals.IsNil && !mode.IncludeUnfactoredAlts())
            {
                return(false);
            }
            else if (unfactoredIntervals.IsNil && !mode.IncludeFactoredAlts())
            {
                return(false);
            }

            if (unfactoredIntervals.IsNil && factoredIntervals.Count == alternatives.Count && mode.IncludeFactoredAlts() && !includeFactoredElement)
            {
                for (int i = 0; i < factoredAlternatives.Length; i++)
                {
                    GrammarAST translatedAlt = factoredAlternatives[i];
                    if (translatedAlt.ChildCount == 0)
                    {
                        adaptor.AddChild(translatedAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                    }

                    adaptor.SetChild(block, i, translatedAlt);
                }

                return(true);
            }
            else if (factoredIntervals.IsNil && unfactoredIntervals.Count == alternatives.Count && mode.IncludeUnfactoredAlts())
            {
                for (int i = 0; i < unfactoredAlternatives.Length; i++)
                {
                    GrammarAST translatedAlt = unfactoredAlternatives[i];
                    if (translatedAlt.ChildCount == 0)
                    {
                        adaptor.AddChild(translatedAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                    }

                    adaptor.SetChild(block, i, translatedAlt);
                }

                return(true);
            }

            if (mode == DecisionFactorMode.FULL_FACTOR)
            {
                return(false);
            }

            /* for a, b, c being arbitrary `element` trees, this block performs
             * this transformation:
             *
             * factoredElement a
             * | factoredElement b
             * | factoredElement c
             * | ...
             *
             * ==>
             *
             * factoredElement (a | b | c | ...)
             */
            GrammarAST newChildren = (GrammarAST)adaptor.Nil();

            for (int i = 0; i < alternatives.Count; i++)
            {
                if (mode.IncludeFactoredAlts() && factoredIntervals.Contains(i))
                {
                    bool combineWithPrevious = i > 0 && factoredIntervals.Contains(i - 1) && (!mode.IncludeUnfactoredAlts() || !unfactoredIntervals.Contains(i - 1));
                    if (combineWithPrevious)
                    {
                        GrammarAST translatedAlt = factoredAlternatives[i];
                        if (translatedAlt.ChildCount == 0)
                        {
                            adaptor.AddChild(translatedAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                        }

                        GrammarAST previous = (GrammarAST)newChildren.GetChild(newChildren.ChildCount - 1);

#if false
                        if (LOGGER.isLoggable(Level.FINE))
                        {
                            LOGGER.log(Level.FINE, previous.ToStringTree());
                            LOGGER.log(Level.FINE, translatedAlt.ToStringTree());
                        }
#endif

                        if (previous.ChildCount == 1 || previous.GetChild(1).Type != ANTLRParser.BLOCK)
                        {
                            GrammarAST newBlock = new BlockAST(adaptor.CreateToken(ANTLRParser.BLOCK, "BLOCK"));
                            GrammarAST newAlt   = new AltAST(adaptor.CreateToken(ANTLRParser.ALT, "ALT"));
                            adaptor.AddChild(newBlock, newAlt);
                            while (previous.ChildCount > 1)
                            {
                                adaptor.AddChild(newAlt, previous.DeleteChild(1));
                            }

                            if (newAlt.ChildCount == 0)
                            {
                                adaptor.AddChild(newAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                            }

                            adaptor.AddChild(previous, newBlock);
                        }

                        if (translatedAlt.ChildCount == 1 || translatedAlt.GetChild(1).Type != ANTLRParser.BLOCK)
                        {
                            GrammarAST newBlock = new BlockAST(adaptor.CreateToken(ANTLRParser.BLOCK, "BLOCK"));
                            GrammarAST newAlt   = new AltAST(adaptor.CreateToken(ANTLRParser.ALT, "ALT"));
                            adaptor.AddChild(newBlock, newAlt);
                            while (translatedAlt.ChildCount > 1)
                            {
                                adaptor.AddChild(newAlt, translatedAlt.DeleteChild(1));
                            }

                            if (newAlt.ChildCount == 0)
                            {
                                adaptor.AddChild(newAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                            }

                            adaptor.AddChild(translatedAlt, newBlock);
                        }

                        GrammarAST combinedBlock = (GrammarAST)previous.GetChild(1);
                        adaptor.AddChild(combinedBlock, translatedAlt.GetChild(1).GetChild(0));

#if false
                        if (LOGGER.isLoggable(Level.FINE))
                        {
                            LOGGER.log(Level.FINE, previous.ToStringTree());
                        }
#endif
                    }
                    else
                    {
                        GrammarAST translatedAlt = factoredAlternatives[i];
                        if (translatedAlt.ChildCount == 0)
                        {
                            adaptor.AddChild(translatedAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                        }

                        adaptor.AddChild(newChildren, translatedAlt);
                    }
                }

                if (mode.IncludeUnfactoredAlts() && unfactoredIntervals.Contains(i))
                {
                    GrammarAST translatedAlt = unfactoredAlternatives[i];
                    if (translatedAlt.ChildCount == 0)
                    {
                        adaptor.AddChild(translatedAlt, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                    }

                    adaptor.AddChild(newChildren, translatedAlt);
                }
            }

            adaptor.ReplaceChildren(block, 0, block.ChildCount - 1, newChildren);

            if (!variant && block.Parent is RuleAST)
            {
                RuleAST            ruleAST   = (RuleAST)block.Parent;
                string             ruleName  = ruleAST.GetChild(0).Text;
                Rule               r         = _rules[ruleName];
                IList <GrammarAST> blockAlts = block.GetAllChildrenWithType(ANTLRParser.ALT);
                r.numberOfAlts = blockAlts.Count;
                r.alt          = new Alternative[blockAlts.Count + 1];
                for (int i = 0; i < blockAlts.Count; i++)
                {
                    r.alt[i + 1]     = new Alternative(r, i + 1);
                    r.alt[i + 1].ast = (AltAST)blockAlts[i];
                }
            }

            return(true);
        }
        /** Build lexer grammar from combined grammar that looks like:
         *
         *  (COMBINED_GRAMMAR A
         *      (tokens { X (= Y 'y'))
         *      (OPTIONS (= x 'y'))
         *      (@ members {foo})
         *      (@ lexer header {package jj;})
         *      (RULES (RULE .+)))
         *
         *  Move rules and actions to new tree, don't dup. Split AST apart.
         *  We'll have this Grammar share token symbols later; don't generate
         *  tokenVocab or tokens{} section.  Copy over named actions.
         *
         *  Side-effects: it removes children from GRAMMAR &amp; RULES nodes
         *                in combined AST.  Anything cut out is dup'd before
         *                adding to lexer to avoid "who's ur daddy" issues
         */
        public virtual GrammarRootAST ExtractImplicitLexer(Grammar combinedGrammar)
        {
            GrammarRootAST combinedAST = combinedGrammar.ast;
            //tool.log("grammar", "before="+combinedAST.toStringTree());
            GrammarASTAdaptor adaptor = new GrammarASTAdaptor(combinedAST.Token.InputStream);

            GrammarAST[] elements = combinedAST.GetChildrenAsArray();

            // MAKE A GRAMMAR ROOT and ID
            string         lexerName = combinedAST.GetChild(0).Text + "Lexer";
            GrammarRootAST lexerAST  =
                new GrammarRootAST(new CommonToken(ANTLRParser.GRAMMAR, "LEXER_GRAMMAR"), combinedGrammar.ast.tokenStream);

            lexerAST.grammarType       = ANTLRParser.LEXER;
            lexerAST.Token.InputStream = combinedAST.Token.InputStream;
            lexerAST.AddChild((ITree)adaptor.Create(ANTLRParser.ID, lexerName));

            // COPY OPTIONS
            GrammarAST optionsRoot =
                (GrammarAST)combinedAST.GetFirstChildWithType(ANTLRParser.OPTIONS);

            if (optionsRoot != null && optionsRoot.ChildCount != 0)
            {
                GrammarAST lexerOptionsRoot = (GrammarAST)adaptor.DupNode(optionsRoot);
                lexerAST.AddChild(lexerOptionsRoot);
                GrammarAST[] options = optionsRoot.GetChildrenAsArray();
                foreach (GrammarAST o in options)
                {
                    string optionName = o.GetChild(0).Text;
                    if (Grammar.lexerOptions.Contains(optionName) &&
                        !Grammar.doNotCopyOptionsToLexer.Contains(optionName))
                    {
                        GrammarAST optionTree = (GrammarAST)adaptor.DupTree(o);
                        lexerOptionsRoot.AddChild(optionTree);
                        lexerAST.SetOption(optionName, (GrammarAST)optionTree.GetChild(1));
                    }
                }
            }

            // COPY all named actions, but only move those with lexer:: scope
            IList <GrammarAST> actionsWeMoved = new List <GrammarAST>();

            foreach (GrammarAST e in elements)
            {
                if (e.Type == ANTLRParser.AT)
                {
                    lexerAST.AddChild((ITree)adaptor.DupTree(e));
                    if (e.GetChild(0).Text.Equals("lexer"))
                    {
                        actionsWeMoved.Add(e);
                    }
                }
            }

            foreach (GrammarAST r in actionsWeMoved)
            {
                combinedAST.DeleteChild(r);
            }

            GrammarAST combinedRulesRoot =
                (GrammarAST)combinedAST.GetFirstChildWithType(ANTLRParser.RULES);

            if (combinedRulesRoot == null)
            {
                return(lexerAST);
            }

            // MOVE lexer rules

            GrammarAST lexerRulesRoot = (GrammarAST)adaptor.Create(ANTLRParser.RULES, "RULES");

            lexerAST.AddChild(lexerRulesRoot);
            IList <GrammarAST> rulesWeMoved = new List <GrammarAST>();

            GrammarASTWithOptions[] rules;
            if (combinedRulesRoot.ChildCount > 0)
            {
                rules = combinedRulesRoot.Children.Cast <GrammarASTWithOptions>().ToArray();
            }
            else
            {
                rules = new GrammarASTWithOptions[0];
            }

            foreach (GrammarASTWithOptions r in rules)
            {
                string ruleName = r.GetChild(0).Text;
                if (Grammar.IsTokenName(ruleName))
                {
                    lexerRulesRoot.AddChild((ITree)adaptor.DupTree(r));
                    rulesWeMoved.Add(r);
                }
            }

            foreach (GrammarAST r in rulesWeMoved)
            {
                combinedRulesRoot.DeleteChild(r);
            }

            // Will track 'if' from IF : 'if' ; rules to avoid defining new token for 'if'
            IList <System.Tuple <GrammarAST, GrammarAST> > litAliases =
                Grammar.GetStringLiteralAliasesFromLexerRules(lexerAST);

            ISet <string> stringLiterals = combinedGrammar.GetStringLiterals();
            // add strings from combined grammar (and imported grammars) into lexer
            // put them first as they are keywords; must resolve ambigs to these rules
            //		tool.log("grammar", "strings from parser: "+stringLiterals);
            int insertIndex = 0;

            foreach (string lit in stringLiterals)
            {
                // if lexer already has a rule for literal, continue
                if (litAliases != null)
                {
                    foreach (System.Tuple <GrammarAST, GrammarAST> pair in litAliases)
                    {
                        GrammarAST litAST = pair.Item2;
                        if (lit.Equals(litAST.Text))
                        {
                            goto continueNextLit;
                        }
                    }
                }
                // create for each literal: (RULE <uniquename> (BLOCK (ALT <lit>))
                string rname = combinedGrammar.GetStringLiteralLexerRuleName(lit);
                // can't use wizard; need special node types
                GrammarAST  litRule = new RuleAST(ANTLRParser.RULE);
                BlockAST    blk     = new BlockAST(ANTLRParser.BLOCK);
                AltAST      alt     = new AltAST(ANTLRParser.ALT);
                TerminalAST slit    = new TerminalAST(new CommonToken(ANTLRParser.STRING_LITERAL, lit));
                alt.AddChild(slit);
                blk.AddChild(alt);
                CommonToken idToken = new CommonToken(ANTLRParser.TOKEN_REF, rname);
                litRule.AddChild(new TerminalAST(idToken));
                litRule.AddChild(blk);
                lexerRulesRoot.InsertChild(insertIndex, litRule);
                //			lexerRulesRoot.getChildren().add(0, litRule);
                lexerRulesRoot.FreshenParentAndChildIndexes(); // reset indexes and set litRule parent

                // next literal will be added after the one just added
                insertIndex++;

continueNextLit:
                ;
            }

            // TODO: take out after stable if slow
            lexerAST.SanityCheckParentAndChildIndexes();
            combinedAST.SanityCheckParentAndChildIndexes();
            //		tool.log("grammar", combinedAST.toTokenString());

            combinedGrammar.tool.Log("grammar", "after extract implicit lexer =" + combinedAST.ToStringTree());
            combinedGrammar.tool.Log("grammar", "lexer =" + lexerAST.ToStringTree());

            if (lexerRulesRoot.ChildCount == 0)
            {
                return(null);
            }
            return(lexerAST);
        }