/*
 ***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * License Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2002 Benoit Cerrina <b.cerrina@wanadoo.fr>
 * Copyright (C) 2002-2004 Anders Bengtsson <ndrsbngtssn@yahoo.se>
 * Copyright (C) 2002-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2004 Charles O Nutter <headius@headius.com>
 * Copyright (C) 2004 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
 * Copyright (C) 2006-2007 Mirko Stocker <me@misto.ch>
 * Copyright (C) 2006 Thomas Corbat <tcorbat@hsr.ch>
 * 
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the EPL, the GPL or the LGPL.
 ***** END LICENSE BLOCK *****/

package org.jruby.parser;

import java.io.IOException;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.jcodings.Encoding;
import org.jcodings.specific.USASCIIEncoding;
import org.jruby.Ruby;
import org.jruby.RubyBignum;
import org.jruby.RubyRegexp;
import org.jruby.RubyString;
import org.jruby.RubySymbol;
import org.jruby.ast.*;
import org.jruby.ast.types.INameNode;
import org.jruby.ast.visitor.OperatorCallNode;
import org.jruby.common.IRubyWarnings;
import org.jruby.common.IRubyWarnings.ID;
import org.jruby.common.RubyWarnings;
import org.jruby.ext.coverage.CoverageData;
import org.jruby.lexer.LexerSource;
import org.jruby.lexer.yacc.LexContext;
import org.jruby.lexer.yacc.RubyLexer;
import org.jruby.lexer.yacc.StackState;
import org.jruby.lexer.yacc.StrTerm;
import org.jruby.runtime.DynamicScope;
import org.jruby.runtime.Signature;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.util.ByteList;
import org.jruby.util.CommonByteLists;
import org.jruby.util.KeyValuePair;
import org.jruby.util.RegexpOptions;
import org.jruby.util.StringSupport;
import org.jruby.util.cli.Options;

import static org.jruby.lexer.LexingCommon.*;
import static org.jruby.lexer.LexingCommon.AMPERSAND_AMPERSAND;
import static org.jruby.lexer.LexingCommon.DOT;
import static org.jruby.lexer.LexingCommon.OR_OR;
import static org.jruby.lexer.LexingCommon.STAR_STAR;
import static org.jruby.lexer.yacc.RubyLexer.Keyword.*;
import static org.jruby.parser.RubyParserBase.IDType.*;
import static org.jruby.util.CommonByteLists.*;
import static org.jruby.util.RubyStringBuilder.*;

/** 
 *
 */
public abstract class RubyParserBase {
    // Parser states:
    protected StaticScope currentScope;
    protected ScopedParserState scopedParserState;

    protected RubyLexer lexer;

    // Should we warn if a variable is declared not actually used?
    private boolean warnOnUnusedVariables;

    private RubyParserResult result;

    public boolean isNextBreak = false;

    public IRubyObject case_labels;

    private Set<ByteList> keyTable;
    private Set<ByteList> variableTable;

    private int maxNumParam = 0;
    private Node numParamCurrent = null;
    private Node numParamInner = null;
    private Node numParamOuter = null;

    private Ruby runtime;

    private DynamicScope existingScope;

    protected ParserType type;

    private int[] coverage = EMPTY_COVERAGE;

    private static final int[] EMPTY_COVERAGE = new int[0];

    private boolean frozenStringLiterals;

    public RubyParserBase(Ruby runtime, LexerSource source, DynamicScope scope, ParserType type) {
        this.runtime = runtime;
        this.lexer = new RubyLexer(this, source, getWarnings());
        this.existingScope = scope;
        this.type = type;
        this.result = new RubyParserResult();
        frozenStringLiterals = runtime.getInstanceConfig().isFrozenStringLiteral();
    }

    public void reset() {
        lexer.getLexContext().reset();
    }

    public StaticScope getCurrentScope() {
        return currentScope;
    }
    
    public void popCurrentScope() {
        if (!currentScope.isBlockScope()) { // blocks are soft scopes. All others are roots of lvars we are leaving.
            lexer.getCmdArgumentState().pop();
            lexer.getConditionState().pop();
        }

        if (warnOnUnusedVariables) {
            scopedParserState.warnUnusedVariables(this, currentScope.getFile());
        }

        currentScope = currentScope.getEnclosingScope();
        scopedParserState = scopedParserState.getEnclosingScope();
    }
    
    public void pushBlockScope() {
        warnOnUnusedVariables = getWarnings().isVerbose();
        currentScope = getRuntime().getStaticScopeFactory().newBlockScope(currentScope, lexer.getFile());
        scopedParserState = new ScopedParserState(scopedParserState);
    }
    
    public void pushLocalScope() {
        warnOnUnusedVariables = getWarnings().isVerbose();
        currentScope = getRuntime().getStaticScopeFactory().newLocalScope(currentScope, lexer.getFile());
        scopedParserState = new ScopedParserState(scopedParserState, lexer.getCmdArgumentState().getStack(), lexer.getConditionState().getStack());
        lexer.getCmdArgumentState().push0();
        lexer.getConditionState().push0();
    }

    public Node numparam_push() {
        Node inner = numParamInner;

        if (numParamOuter == null) numParamOuter = numParamCurrent;

        numParamInner = null;
        numParamCurrent = null;

        return inner;
    }

    public void numparam_pop(Node previousInner) {
        if (previousInner != null) {
            numParamInner = previousInner;
        } else if (numParamCurrent != null) {
            numParamInner = numParamCurrent;
        }

        if (maxNumParam > 0) {
            numParamCurrent = numParamOuter;
            numParamOuter = null;
        } else {
            numParamCurrent = null;
        }

    }

    public ArgsNode args_with_numbered(ArgsNode args, int paramCount) {
        if (paramCount > 0) {
            if (args == null) { // FIXME: I think this is not possible.
                ListNode pre = makePreNumArgs(paramCount);
                args = new_args(lexer.getRubySourceline(), pre, null, null, null, null);
            } else if (args.getArgs().length == 0) {
                ListNode pre = makePreNumArgs(paramCount);
                args = new_args(lexer.getRubySourceline(), pre, null, null, null, null);
            } else {
                // FIXME: not sure where errors are printed in all this but could be here.
            }
            // FIXME: it just sets pre-value here but what existing args node would work here?
        }
        return args;
    }

    private ListNode makePreNumArgs(int paramCount) {
        ListNode list = new ArrayNode(lexer.getRubySourceline());

        for (int i = 1; i <= paramCount; i++) {
            RubySymbol name = symbolID(new ByteList(("_" + i).getBytes()));
            list.add(new ArgumentNode(lexer.getRubySourceline(), name, getCurrentScope().addVariableThisScope(name.idString())));
        }

        return list;
    }

    public int resetMaxNumParam() {
        return restoreMaxNumParam(0);
    }

    public int restoreMaxNumParam(int maxNum) {
        int temp = maxNumParam;

        maxNumParam = maxNum;

        return temp;
    }

    public void ordinalMaxNumParam() {
        maxNumParam = -1;
    }
    
    public static Node arg_concat(Node node1, Node node2) {
        return node2 == null ? node1 : new ArgsCatNode(node1.getLine(), node1, node2);
    }

    // firstNode is ArgsCatNode, SplatNode, ArrayNode, HashNode
    // secondNode is null or not
    public static Node arg_blk_pass(Node firstNode, BlockPassNode secondNode) {
        if (secondNode != null) {
            secondNode.setArgsNode(firstNode);
            return secondNode;
        }
        return firstNode;
    }

    /**
     * We know for callers of this that it cannot be any of the specials checked in gettable.
     * 
     * @param node to check its variable type
     * @return an AST node representing this new variable
     */
    public Node gettable2(Node node) {
        switch (node.getNodeType()) {
        case DASGNNODE: // LOCALVAR
        case LOCALASGNNODE:
            RubySymbol name = ((INameNode) node).getName();
            String id = name.idString();
            int slot = currentScope.isDefined(id);

            if (currentScope.isBlockScope() && slot != -1) {
                if (isNumParamId(id) && isNumParamNested()) return null;
                if (name.getBytes().equals(lexer.getCurrentArg())) {
                    compile_error(str(getRuntime(), "circular argument reference - ", name));
                }

                Node newNode = new DVarNode(node.getLine(), slot, name);

                if (warnOnUnusedVariables && newNode instanceof IScopedNode) {
                    scopedParserState.markUsedVariable(name, ((IScopedNode) node).getDepth());
                }
                return newNode;
            }

            StaticScope.Type type = currentScope.getType();
            if (type == StaticScope.Type.LOCAL) {
                if (name.getBytes().equals(lexer.getCurrentArg())) {
                    compile_error(str(getRuntime(), "circular argument reference - ", name));
                }

                Node newNode = new LocalVarNode(node.getLine(), slot, name);

                if (warnOnUnusedVariables && newNode instanceof IScopedNode) {
                    scopedParserState.markUsedVariable(name, ((IScopedNode) node).getDepth());
                }

                return newNode;
            }
            if (type == StaticScope.Type.BLOCK && isNumParamId(id) && numberedParam(id)) {
                if (isNumParamNested()) return null;

                Node newNode = new DVarNode(node.getLine(), slot, name);
                if (numParamCurrent == null) numParamCurrent = newNode;
                return newNode;
            }
            if (currentScope.getType() != StaticScope.Type.BLOCK) numparam_name(name.getBytes());

            return new VCallNode(node.getLine(), name);
        case CONSTDECLNODE: // CONSTANT
            return new ConstNode(node.getLine(), ((INameNode) node).getName());
        case INSTASGNNODE: // INSTANCE VARIABLE
            return new InstVarNode(node.getLine(), ((INameNode) node).getName());
        case CLASSVARDECLNODE:
        case CLASSVARASGNNODE:
            return new ClassVarNode(node.getLine(), ((INameNode) node).getName());
        case GLOBALASGNNODE:
            return new GlobalVarNode(node.getLine(), ((INameNode) node).getName());
        }

        getterIdentifierError(((INameNode) node).getName());
        return null;
    }

    private boolean numberedParam(String id) {
        int n = Integer.parseInt(id.substring(1));
        if (scopedParserState.getEnclosingScope() == null) return false;

        if (maxNumParam == -1) {
            compile_error("ordinary parameter is defined");
            return false;
        }

        // if we have proc { _3 } then we need to up to 3 even though we never reference _1 or _2.
        if (maxNumParam < n) maxNumParam = n;

        // MRI adds to their vtable here but we do it in makePreNumArgs.  We are just
        // making them like legit params and IRBuilder will be none the wiser.

        return true;
    }

    private boolean isNumParamNested() {
        if (numParamOuter == null && numParamInner == null) return false;

        Node used = numParamOuter != null ? numParamOuter : numParamInner;
        compile_error("numbered parameter is already used in\n" + lexer.getFile() + ":" + used.getLine() + ": " +
                (numParamOuter != null ? "outer" : "inner") + " block here");
        // FIXME: Show error line
        return true;
    }

    private boolean isNumParamId(String id) {
        if (id.length() != 2 || id.charAt(0) != '_') return false;

        char one = id.charAt(1);
        return one != '0' && Character.isDigit(one); // _1..._9
    }

    // FIXME: We probably only need one impl of this method.
    public void numparam_name(RubySymbol name) {
        numparam_name(name.getBytes());
    }
    public void numparam_name(ByteList name) {
        // FIXME: probably make isNumParamId with ByteList.
        String id = name.toString();
        if (isNumParamId(id)) compile_error(id + " is reserved for numbered parameter");
    }

    public Node declareIdentifier(ByteList byteName) {
        RubySymbol name = symbolID(byteName);
        if (byteName.equals(lexer.getCurrentArg())) {
            compile_error(str(getRuntime(), "circular argument reference - ", name));
        }

        String id = name.idString();
        boolean isNumParam = isNumParamId(id);

        Node node;
        int slot;
        if (isNumParam && numberedParam(id)) {
            if (isNumParamNested()) return null;

            // We go over the top here and make sure the order is always ascending even if the other
            // numbered params are not used. This is so local_variables will properly display in
            // ascending order.
            makePreNumArgs(Integer.parseInt(id.substring(1)));

            slot = currentScope.addVariable(id);
            node = currentScope.isBlockScope() ?
                    new DVarNode(lexer.tokline, slot, name) :
                    new LocalVarNode(lexer.tokline, slot, name);
            if (numParamCurrent == null) numParamCurrent = node;
        }  else {
            node = currentScope.declare(lexer.tokline, name);
            slot = currentScope.isDefined(id); // FIXME: we should not do this extra call.
        }

        if (warnOnUnusedVariables && node instanceof IScopedNode) addOrMarkVariable(name, slot);

        return node;
    }

    public boolean isArgsInfoEmpty(ArgsNode argsNode) {
        return argsNode.isEmpty();
    }

    // We know it has to be tLABEL or tIDENTIFIER so none of the other assignable logic is needed
    public AssignableNode assignableLabelOrIdentifier(ByteList byteName, Node value) {
        RubySymbol name = symbolID(byteName);

        numparam_name(byteName);

        if (warnOnUnusedVariables) addOrMarkVariable(name, currentScope.isDefined(name.idString()));

        return currentScope.assign(lexer.getRubySourceline(), name, makeNullNil(value));
    }

    private void addOrMarkVariable(RubySymbol name, int slot) {
        if (slot == -1) {
            scopedParserState.addDefinedVariable(name, lexer.getRubySourceline());
        } else {
            scopedParserState.markUsedVariable(name, slot >> 16);
        }
    }

    // We know it has to be tLABEL or tIDENTIFIER so none of the other assignable logic is needed
    public AssignableNode assignableKeyword(ByteList name, Node value) {
        return currentScope.assignKeyword(lexer.getRubySourceline(), symbolID(name), makeNullNil(value));
    }
    
    protected void getterIdentifierError(RubySymbol identifier) {
        lexer.compile_error("identifier " + identifier + " is not valid to get");
    }

    /**
     *  Wraps node with NEWLINE node.
     *
     */
    public Node newline_node(Node node, int line) {
        if (node == null) return null;

        Node newNode = remove_begin(node);
        // Conservative fix...try and use line unless we see remove has been removed then use the newNode.
        if (newNode != node) line = newNode.getLine();
        coverLine(line);
        node.setNewline();

        return node;
    }

    // This is the last node made in the AST unintuitively so so post-processing can occur here.
    public Node addRootNode(Node topOfAST) {
        int line;
        CoverageData coverageData = finishCoverage(lexer.getFile(), lexer.lineno());
        if (result.getBeginNodes().isEmpty()) {
            if (topOfAST == null) {
                topOfAST = NilImplicitNode.NIL;
                line = lexer.getRubySourceline();
            } else {
                line = topOfAST.getLine();
            }
        } else {
            line = topOfAST != null ? topOfAST.getLine() : result.getBeginNodes().get(0).getLine();
            BlockNode newTopOfAST = new BlockNode(line);
            for (Node beginNode : result.getBeginNodes()) {
                appendToBlock(newTopOfAST, beginNode);
            }

            // Add real top to new top (unless this top is empty [only begin/end nodes or truly empty])
            if (topOfAST != null) newTopOfAST.add(topOfAST);
            topOfAST = newTopOfAST;
        }

        int coverageMode = coverageData == null ?
                CoverageData.NONE :
                coverageData.getMode();

        return new RootNode(line, result.getScope(), topOfAST, lexer.getFile(), coverageMode);
    }
    
    /* MRI: block_append */
    public Node appendToBlock(Node head, Node tail) {
        if (tail == null) return head;
        if (head == null) return tail;

        switch (head.getNodeType()) {
            case BIGNUMNODE: case FIXNUMNODE: case FLOATNODE: // NODE_LIT
            case STRNODE: case SELFNODE: case TRUENODE: case FALSENODE: case NILNODE:
                if (!(head instanceof InvisibleNode)) warning(ID.MISCELLANEOUS, lexer.getFile(), tail.getLine(), "unused literal ignored");
                return tail;
        }

        if (!(head instanceof BlockNode)) {
            head = new BlockNode(head.getLine()).add(head);
        }

        if (getWarnings().isVerbose() && isBreakStatement(((ListNode) head).getLast()) && Options.PARSER_WARN_NOT_REACHED.load()) {
            warning(ID.STATEMENT_NOT_REACHED, lexer.getFile(), tail.getLine(), "statement not reached");
        }

        // Assumption: tail is never a list node
        ((ListNode) head).addAll(tail);
        return head;
    }

    // We know it has to be tLABEL or tIDENTIFIER so none of the other assignable logic is needed
    public AssignableNode assignableInCurr(ByteList nameBytes, Node value) {
        RubySymbol name = symbolID(nameBytes);
        currentScope.addVariableThisScope(name.idString());
        if (warnOnUnusedVariables) scopedParserState.addDefinedVariable(name, lexer.getRubySourceline());
        return currentScope.assign(lexer.getRubySourceline(), name, makeNullNil(value));
    }

    public Node call_uni_op(Node firstNode, ByteList operator) {
        value_expr(firstNode);

        return new OperatorCallNode(firstNode.getLine(), firstNode, symbolID(operator), null, null, false);
    }
    
    public Node call_bin_op(Node firstNode, ByteList operator, Node secondNode) {
        return getOperatorCallNodeInner(firstNode, operator, secondNode);
    }

    public Node call_bin_op(Node firstNode, ByteList operator, Node secondNode, int defaultPosition) {
        firstNode = checkForNilNode(firstNode, defaultPosition);
        secondNode = checkForNilNode(secondNode, defaultPosition);

        return getOperatorCallNodeInner(firstNode, operator, secondNode);
    }

    private Node getOperatorCallNodeInner(Node firstNode, ByteList operator, Node secondNode) {
        value_expr(firstNode);
        value_expr(secondNode);

        return new OperatorCallNode(firstNode.getLine(), firstNode, symbolID(operator), new ArrayNode(secondNode.getLine(), secondNode), null, false);
    }

    public Node new_defined(long line, Node node) {
        return new DefinedNode((int) line, node);
    }

    public Node match_op(Node firstNode, Node secondNode) {
        if (firstNode instanceof DRegexpNode) {
            return new Match2Node(firstNode.getLine(), firstNode, secondNode);
        } else if (firstNode instanceof RegexpNode) {
            List<Integer> locals = allocateNamedLocals((RegexpNode) firstNode);

            if (locals.size() > 0) {
                int[] primitiveLocals = new int[locals.size()];
                for (int i = 0; i < primitiveLocals.length; i++) {
                    primitiveLocals[i] = locals.get(i);
                }
                return new Match2CaptureNode(firstNode.getLine(), firstNode, secondNode, primitiveLocals);
            } else {
                return new Match2Node(firstNode.getLine(), firstNode, secondNode);
            }
        } else if (secondNode instanceof DRegexpNode || secondNode instanceof RegexpNode) {
            return new Match3Node(firstNode.getLine(), firstNode, secondNode);
        }

        return call_bin_op(firstNode, CommonByteLists.EQUAL_TILDE, secondNode);
    }

    /**
     * Define an array set condition so we can return lhs
     * 
     * @param receiver array being set
     * @param index node which should evalute to index of array set
     * @return an AttrAssignNode
     */
    public Node aryset(Node receiver, Node index) {
        value_expr(receiver);

        return new_attrassign(receiver.getLine(), receiver, CommonByteLists.ASET_METHOD, index, false);
    }

    /**
     * Define an attribute set condition so we can return lhs
     * 
     * @param receiver object which contains attribute
     * @param name of the attribute being set
     * @return an AttrAssignNode
     */
    public Node attrset(Node receiver, ByteList name) {
        return attrset(receiver, DOT, name);
    }

    public Node attrset(Node receiver, ByteList callType, ByteList name) {
        return new_attrassign(receiver.getLine(), receiver, name.append('='), null, isLazy(callType));
    }

    public void backrefAssignError(Node node) {
        if (node instanceof NthRefNode) {
            String varName = "$" + ((NthRefNode) node).getMatchNumber();
            lexer.compile_error("Can't set variable " + varName + '.');
        } else if (node instanceof BackRefNode) {
            String varName = "$" + ((BackRefNode) node).getType();
            lexer.compile_error("Can't set variable " + varName + '.');
        }
    }

    private static Node arg_add(int line, Node node1, Node node2) {
        if (node1 == null) {
            if (node2 == null) {
                return new ArrayNode(line, NilImplicitNode.NIL);
            } else {
                return new ArrayNode(node2.getLine(), node2);
            }
        }
        if (node1 instanceof ArrayNode) return ((ArrayNode) node1).add(node2);
        
        return new ArgsPushNode(line, node1, node2);
    }
    
	/**
	 **/
    public static Node node_assign(Node lhs, Node rhs) {
        if (lhs == null) return null;

        // MRI sets position to one passed in its version of node_assign but it is always pos of lhs????
        if (lhs instanceof AssignableNode) {
    	    ((AssignableNode) lhs).setValueNode(rhs);
        } else if (lhs instanceof IArgumentNode) {
            IArgumentNode invokableNode = (IArgumentNode) lhs;
            
            return invokableNode.setArgsNode(arg_add(lhs.getLine(), invokableNode.getArgsNode(), rhs));
        }
        
        return lhs;
    }
    
    public Node ret_args(Node node, int line) {
        if (node != null) {
            if (node instanceof BlockPassNode) {
                lexer.compile_error("block argument should not be given");
            } else if (node instanceof ArrayNode && ((ArrayNode)node).size() == 1) {
                node = ((ArrayNode)node).get(0);
            } else if (node instanceof SplatNode) {
                node = newSValueNode(line, node);
            }
        }

        if (node == null) node = NilImplicitNode.NIL;
        
        return node;
    }

    private static boolean isBreakStatement(Node node) {
        if (node == null) return false;

        switch (node.getNodeType()) {
            case BREAKNODE: case NEXTNODE: case REDONODE:
            case RETRYNODE: case RETURNNODE:
                return true;
            default:
                return false;
        }
    }
    
    public void warnUnlessEOption(ID id, Node node, String message) {
        if (!isInline()) warning(id, lexer.getFile(), node.getLine(), message);
    }

    private boolean isInline() {
        return type == ParserType.INLINE;
    }

    boolean value_expr_check(Node node) {
        boolean void_node = false;

        if (node == null) warn(lexer.getRubySourceline(), "empty expression");

        while (node != null) {
            switch (node.getNodeType()) {
                case RETURNNODE: case BREAKNODE: case NEXTNODE: case REDONODE: case RETRYNODE:
                    return void_node ? void_node : true;
                case PATTERNCASENODE: {
                    Node[] cases = ((PatternCaseNode) node).getCases();
                    if (cases != null && cases.length > 0 && cases[0] != null) {
                        return false;
                    }
                    /* single line pattern matching */
                    return void_node ? void_node : true;
                }
                case BLOCKNODE:
                    node = ((BlockNode) node).getLast();
                    break;
                case BEGINNODE:
                    node = ((BeginNode) node).getBodyNode();
                    break;
                case IFNODE:
                    if (((IfNode) node).getThenBody() == null) return false;
                    if (((IfNode) node).getElseBody() == null) return false;

                    boolean vn = value_expr_check(((IfNode) node).getThenBody());
                    if (!vn) return false;
                    if (!void_node) void_node = vn;
                    node = ((IfNode) node).getElseBody();
                    break;
                case ANDNODE: case ORNODE:
                    node = ((BinaryOperatorNode) node).getFirstNode();
                    break;
                case LOCALASGNNODE: case DASGNNODE: // FIXME: MASGN should also mark unknown variables.
                    if (warnOnUnusedVariables) {
                        scopedParserState.markUsedVariable((((INameNode) node).getName()), (((IScopedNode) node).getDepth()));
                    }
                    return false;
                default:
                    return false;
            }
        }

        return false;
    }


    public boolean value_expr(Node node) {
        boolean void_expr = value_expr_check(node);

        if (void_expr) lexer.compile_error("void value expression");

        return void_expr;
    }

    private void handleUselessWarn(Node node, String useless) {
        if (Options.PARSER_WARN_USELESSS_USE_OF.load()) {
            warn(node.getLine(), "possibly useless use of " + useless + " in void context");
        }
    }

    /**
     * Check to see if current node is an useless statement.  If useless a warning if printed.
     * 
     * @param node to be checked.
     */
    public void void_expr(Node node) {
        if (!getWarnings().isVerbose()) return;
        
        if (node == null) return;
            
        switch (node.getNodeType()) {
            case CALLNODE: {
                if (!(node instanceof OperatorCallNode)) return;
                ByteList name = ((CallNode) node).getName().getBytes();
                int length = name.realSize();

                if (length > 3) {
                    return;
                } else if (length == 3) {
                    if (name.charAt(0) == '<' || name.charAt(1) == '=' || name.charAt(2) == '>') {
                        handleUselessWarn(node, name.toString());
                    }
                    return;
                }

                boolean isUseless = false;
                switch (name.charAt(0)) {
                    case '+': case '-':
                        if (length == 1 || name.charAt(1) == '@') isUseless = true;
                        break;
                    case '*':
                        if (length == 1 || name.charAt(1) == '*') isUseless = true;
                        break;
                    case '/': case '%': case '|': case '^': case '&':
                        if (length == 1) isUseless = true;
                        break;
                    case '<': case '>': case '=':
                        if (length == 1 || name.charAt(1) == '=') isUseless = true;
                        break;

                    case '!':
                        if (length > 1 && name.charAt(1) == '=') isUseless = true;
                        break;
                }

                if (isUseless) handleUselessWarn(node, name.toString());

                return;
            }
            case BACKREFNODE: case DVARNODE: case GLOBALVARNODE:
            case LOCALVARNODE: case NTHREFNODE: case CLASSVARNODE:
            case INSTVARNODE:
                handleUselessWarn(node, "a variable"); return;
            case CONSTNODE:
                handleUselessWarn(node, "a constant"); return;
            case BIGNUMNODE: case DREGEXPNODE: case DSTRNODE: case DSYMBOLNODE:
            case FIXNUMNODE: case FLOATNODE: case REGEXPNODE:
            case STRNODE: case SYMBOLNODE:
                handleUselessWarn(node, "a literal"); return;
            case COLON2NODE: case COLON3NODE:
                handleUselessWarn(node, "::"); return;
            case DOTNODE:
                handleUselessWarn(node, ((DotNode) node).isExclusive() ? "..." : ".."); return;
            case SELFNODE:
                handleUselessWarn(node, "self"); return;
            case NILNODE:
                handleUselessWarn(node, "nil"); return;
            case FALSENODE:
                handleUselessWarn(node, "false"); return;
            case TRUENODE:
                handleUselessWarn(node, "true"); return;
            case DEFINEDNODE:
                handleUselessWarn(node, "defined?"); return;
        }
    }

    public Node gettable(ByteList id) {
        int loc = lexer.getRubySourceline();
        if (id.equals(SELF)) return new SelfNode(loc);
        if (id.equals(NIL)) return new NilNode(loc);
        if (id.equals(TRUE)) return new TrueNode(loc);
        if (id.equals(FALSE)) return new FalseNode(loc);
        if (id.equals(__FILE__)) return new FileNode(loc, new ByteList(lexer.getFile().getBytes()));
        if (id.equals(__LINE__)) return new FixnumNode(loc, loc);
        if (id.equals(__ENCODING__)) return new EncodingNode(loc, lexer.getEncoding());

        RubySymbol name = symbolID(id);

        switch (id_type(id)) {
            case Local: {
                String id2 = name.idString();
                int slot = currentScope.isDefined(id2);

                if (currentScope.isBlockScope() && slot != -1) {
                    if (isNumParamId(id2) && isNumParamNested()) return null;
                    if (name.getBytes().equals(lexer.getCurrentArg())) {
                        compile_error(str(getRuntime(), "circular argument reference - ", name));
                    }

                    Node newNode = new DVarNode(loc, slot, name);

                    if (warnOnUnusedVariables && newNode instanceof IScopedNode) {
                        scopedParserState.markUsedVariable(name, ((IScopedNode) newNode).getDepth());
                    }
                    return newNode;
                }

                StaticScope.Type type = currentScope.getType();
                if (type == StaticScope.Type.LOCAL && slot != -1) {
                    if (name.getBytes().equals(lexer.getCurrentArg())) {
                        compile_error(str(getRuntime(), "circular argument reference - ", name));
                    }

                    Node newNode = new LocalVarNode(loc, slot, name);

                    if (warnOnUnusedVariables && newNode instanceof IScopedNode) {
                        scopedParserState.markUsedVariable(name, ((IScopedNode) newNode).getDepth());
                    }

                    return newNode;
                }
                if (type == StaticScope.Type.BLOCK && isNumParamId(id2) && numberedParam(id2)) {
                    if (isNumParamNested()) return null;

                    Node newNode = new DVarNode(loc, slot, name);
                    if (numParamCurrent == null) numParamCurrent = newNode;
                    return newNode;
                }
                if (currentScope.getType() != StaticScope.Type.BLOCK) numparam_name(id);

                return new VCallNode(loc, name);
            }
            case Global: return new GlobalVarNode(loc, name);
            case Instance: return new InstVarNode(loc, name);
            case Constant: return new ConstNode(loc, name);
            case Class: return new ClassVarNode(loc, name);
            default:
                compile_error("identifier " + id + " is not valid to get");
        }


        return null;
    }

    /**
     * Check all nodes but the last one in a BlockNode for useless (void context) statements.
     * 
     * @param node to be checked.
     */
    public Node void_stmts(Node node) {
        if (!getWarnings().isVerbose() || !(node instanceof BlockNode)) return node;

        BlockNode blockNode = (BlockNode) node;
        int size = blockNode.size();

        for (int i = 0; i <= size - 2; i++) {
            void_expr(blockNode.get(i));
        }

        return node;
    }

	/**
     * assign_in_cond
	 **/
    private boolean checkAssignmentInCondition(Node node) {
        if (node instanceof MultipleAsgnNode || node instanceof LocalAsgnNode || node instanceof DAsgnNode || node instanceof GlobalAsgnNode || node instanceof InstAsgnNode) {
            Node valueNode = ((AssignableNode) node).getValueNode();
            if (isStaticContent(valueNode)) {
                warning(ID.ASSIGNMENT_IN_CONDITIONAL, lexer.getFile(), valueNode.getLine(), "found `= literal' in conditional, should be ==");
            }
            return true;
        } 

        return false;
    }

    // Only literals or does it contain something more dynamic like variables?
    private static boolean isStaticContent(Node node) {
        if (node instanceof HashNode) {
            HashNode hash = (HashNode) node;
            for (KeyValuePair<Node, Node> pair : hash.getPairs()) {
                if (!isStaticContent(pair.getKey()) || !isStaticContent(pair.getValue())) return false;
            }
            return true;
        } else if (node instanceof ArrayNode) {
            ArrayNode array = (ArrayNode) node;
            int size = array.size();

            for (int i = 0; i < size; i++) {
                if (!isStaticContent(array.get(i))) return false;
            }
            return true;
        }

        return node instanceof LiteralValue || node instanceof NilNode || node instanceof TrueNode || node instanceof FalseNode;
    }
    
    protected Node makeNullNil(Node node) {
        return node == null ? NilImplicitNode.NIL : node;
    }

    private Node cond0(Node node, ConditionType type) {
        checkAssignmentInCondition(node);

        if (node == null) return new NilNode(lexer.getRubySourceline());
        
        Node leftNode;
        Node rightNode;

        switch(node.getNodeType()) {
            case DSTRNODE:
            case EVSTRNODE:
            case STRNODE:
                switchByCondTypeWarn(type, node.getLine(), "string ");
                break;
            case DREGEXPNODE: {
                int line = node.getLine();

                if (!isInline()) switchByCondTypeWarning(type, node.getLine(), "regex ");

                return new Match2Node(line, node, new GlobalVarNode(line, symbolID(DOLLAR_UNDERSCORE)));
            }
            case ANDNODE:
                leftNode = cond0(((AndNode) node).getFirstNode(), ConditionType.IN_COND);
                rightNode = cond0(((AndNode) node).getSecondNode(), ConditionType.IN_COND);
            
                return new AndNode(node.getLine(), makeNullNil(leftNode), makeNullNil(rightNode));
            case ORNODE:
                leftNode = cond0(((OrNode) node).getFirstNode(), ConditionType.IN_COND);
                rightNode = cond0(((OrNode) node).getSecondNode(), ConditionType.IN_COND);
            
                return new OrNode(node.getLine(), makeNullNil(leftNode), makeNullNil(rightNode));
            case DOTNODE: {
                DotNode dotNode = (DotNode) node;

                // FIXME: I think we can delete this
                ByteList label = new ByteList(new byte[] {'F', 'L', 'I', 'P'}, USASCII_ENCODING);
                label.append(Long.toString(node.hashCode()).getBytes());
                RubySymbol symbolID = symbolID(label);

                Node begin = range_op(((DotNode) node).getBeginNode());
                Node end = range_op(((DotNode) node).getEndNode());

                return new FlipNode(node.getLine(), begin, end,
                        dotNode.isExclusive(), currentScope.getLocalScope().addVariable(symbolID.idString()));
            }
            case SYMBOLNODE:
            case DSYMBOLNODE:
                switchByCondTypeWarning(type, node.getLine(), "symbol ");
            case REGEXPNODE:
                if (Options.PARSER_WARN_REGEX_CONDITION.load()) {
                    if (!isInline()) switchByCondTypeWarn(type, node.getLine(), "regex ");
                }
                return new MatchNode(node.getLine(), node);
            case FIXNUMNODE:
                switchByCondTypeWarning(type, node.getLine(), "");
                break;

        }

        return node;
    }

    private void switchByCondTypeWarning(ConditionType type, int line, String string) {
        switch(type) {
            case IN_COND:
                warning(line, string + "literal in condition");
                break;
            case IN_FF:
                warning(line, string + "literal in flip-flop");
                break;
        }
    }

    private void switchByCondTypeWarn(ConditionType type, int line, String string) {
        switch(type) {
            case IN_COND:
                warn(line, string + "literal in condition");
                break;
            case IN_FF:
                warn(line, string + "literal in flip-flop");
                break;
        }
    }

    public Node cond(Node node) {
        return cond0(node, ConditionType.IN_COND);
    }

    public Node method_cond(Node node) {
        return cond0(node, ConditionType.IN_OP);
    }

    // we just reverse then/else for unless
    public Node new_if(int line, Node condition, Node thenNode, Node elseNode) {
        if (condition == null) return elseNode;

        condition = cond0(condition, ConditionType.IN_COND);

        return new IfNode(line, condition, thenNode, elseNode);
    }

    enum ConditionType {
        IN_OP, IN_COND, IN_FF;
    }

    /* MRI: range_op */
    private Node range_op(Node node) {
        if (node == null) return null;

        value_expr(node);
        if (node instanceof FixnumNode) {
            warnUnlessEOption(ID.LITERAL_IN_CONDITIONAL_RANGE, node, "integer literal in flip-flop");
            return call_bin_op(node, EQ_EQ, new GlobalVarNode(node.getLine(), symbolID(DOLLAR_DOT)));
        } 

        return cond0(node, ConditionType.IN_FF);
    }

    public SValueNode newSValueNode(int line, Node node) {
        return new SValueNode(line, node);
    }

    // note: node is from arg_value and will be implicit nil or a real node.
    public SplatNode newSplatNode(Node node) {
        int line = node instanceof NilImplicitNode ? lexer.getRubySourceline() : node.getLine();
        return new SplatNode(line, node);
    }

    // FIXME: audit all callers and see if we can remove makeNullNil here (we deplicate both line and makeNullNil on occasions.
    public ArrayNode newArrayNode(int line, Node node) {
        node = makeNullNil(node);
        line = node instanceof NilImplicitNode ? lexer.getRubySourceline() : node.getLine();

        return new ArrayNode(line, node);
    }

    public int position(Node one, Node two) {
        return one == null ? two.getLine() : one.getLine();
    }

    public Node logop(Node left, ByteList op, Node right) {
        value_expr(left);

        if (op == AND_KEYWORD || op == AMPERSAND_AMPERSAND) {
            if (left == null && right == null) return new AndNode(lexer.getRubySourceline(), makeNullNil(left), makeNullNil(right));

            return new AndNode(position(left, right), makeNullNil(left), makeNullNil(right));
        }
        if (left == null && right == null) return new OrNode(lexer.getRubySourceline(), makeNullNil(left), makeNullNil(right));

        return new OrNode(position(left, right), makeNullNil(left), makeNullNil(right));
    }

    /**
     * We post-process a chain of when nodes and analyze them to re-insert them back into our new CaseNode
     * as a list.  The grammar is more amenable to linked list style so we correct it at this point.
     *
     * @param expression of the case node (e.g. case foo)
     * @param firstWhenNode first when (which could also be the else)
     * @return a new case node
     */
    public static CaseNode newCaseNode(int line, Node expression, Node firstWhenNode) {
        ArrayNode cases = new ArrayNode(firstWhenNode != null ? firstWhenNode.getLine() : line);
        CaseNode caseNode = new CaseNode(line, expression, cases);

        for (Node current = firstWhenNode; current != null; current = ((WhenNode) current).getNextCase()) {
            if (current instanceof WhenOneArgNode) {
                cases.add(current);
            } else if (current instanceof WhenNode) {
                simplifyMultipleArgumentWhenNodes((WhenNode) current, cases);
            } else {
                caseNode.setElseNode(current);
                break;
            }
        }

        return caseNode;
    }

    public static PatternCaseNode newPatternCaseNode(int line, Node expression, Node firstWhenNode) {
        ArrayNode cases = new ArrayNode(firstWhenNode != null ? firstWhenNode.getLine() : line);
        PatternCaseNode caseNode = new PatternCaseNode(line, expression, cases);

        for (Node current = firstWhenNode; current != null; current = ((InNode) current).getNextCase()) {
            if (current instanceof InNode) {
                cases.add(current);
            } else {
                caseNode.setElseNode(current);
                break;
            }
        }

        return caseNode;
    }

    /*
     * This method exists for us to break up multiple expression when nodes (e.g. when 1,2,3:)
     * into individual whenNodes.  The primary reason for this is to ensure lazy evaluation of
     * the arguments (when foo,bar,gar:) to prevent side-effects.  In the old code this was done
     * using nested when statements, which was awful for interpreter and compilation.
     *
     * Notes: This has semantic equivalence but will not be lexically equivalent.  Compiler
     * needs to detect same bodies to simplify bytecode generated.
     */
    private static void simplifyMultipleArgumentWhenNodes(WhenNode sourceWhen, ArrayNode cases) {
        Node expressionNodes = sourceWhen.getExpressionNodes();

        if (expressionNodes instanceof SplatNode || expressionNodes instanceof ArgsCatNode) {
            cases.add(sourceWhen);
            return;
        }

        if (expressionNodes instanceof ListNode) {
            ListNode list = (ListNode) expressionNodes;
            int line = sourceWhen.getLine();
            Node bodyNode = sourceWhen.getBodyNode();

            for (int i = 0; i < list.size(); i++) {
                Node expression = list.get(i);

                if (expression instanceof SplatNode || expression instanceof ArgsCatNode) {
                    cases.add(new WhenNode(line, expression, bodyNode, null));
                } else {
                    cases.add(new WhenOneArgNode(line, expression, bodyNode, null));
                }
            }
        } else {
            cases.add(sourceWhen);
        }
    }
    
    public WhenNode newWhenNode(int line, Node expressionNodes, Node bodyNode, Node nextCase) {
        if (bodyNode == null) bodyNode = NilImplicitNode.NIL;

        if (expressionNodes instanceof SplatNode || expressionNodes instanceof ArgsCatNode || expressionNodes instanceof ArgsPushNode) {
            return new WhenNode(line, expressionNodes, bodyNode, nextCase);
        }

        ListNode list = (ListNode) expressionNodes;

        if (list.size() == 1) {
            Node element = list.get(0);
            
            if (!(element instanceof SplatNode)) {
                return new WhenOneArgNode(line, element, bodyNode, nextCase);
            }
        }

        return new WhenNode(line, expressionNodes, bodyNode, nextCase);
    }

    public Node new_op_assign(AssignableNode receiverNode, ByteList operatorName, Node valueNode) {
        int line = receiverNode.getLine();

        if (operatorName == OR_KEYWORD || operatorName == OR_OR) {
            receiverNode.setValueNode(valueNode);
            return new OpAsgnOrNode(line, gettable2(receiverNode), receiverNode);
        } else if (operatorName == AND_KEYWORD || operatorName == AMPERSAND_AMPERSAND) {
            receiverNode.setValueNode(valueNode);
            return new OpAsgnAndNode(line, gettable2(receiverNode), receiverNode);
        } else {
            receiverNode.setValueNode(call_bin_op(gettable2(receiverNode), operatorName, valueNode));
            receiverNode.setLine(line);
            return receiverNode;
        }
    }

    public Node new_ary_op_assign(Node receiverNode, ByteList operatorName, Node argsNode, Node valueNode) {
        int line = lexer.tokline;

        // We extract BlockPass from tree and insert it as a block node value (MRI wraps it around the args)
        Node blockNode = null;
        if (argsNode instanceof BlockPassNode) {
            blockNode = argsNode; // It is weird to leave this as-is but we need to know it vs iternode vs weird ast bug.
            argsNode = ((BlockPassNode) argsNode).getArgsNode();
        }

        Node newNode = new OpElementAsgnNode(line, receiverNode, symbolID(operatorName), argsNode, valueNode, blockNode);
        fixpos(newNode, receiverNode);

        return newNode;
    }

    public Node new_attr_op_assign(Node receiverNode, ByteList callType, Node valueNode, ByteList variableName, ByteList operatorName) {
        return new OpAsgnNode(receiverNode.getLine(), receiverNode, valueNode, symbolID(variableName), symbolID(operatorName), isLazy(callType));
    }

    public Node new_const_op_assign(int line, Node lhs, ByteList operatorName, Node rhs) {
        // FIXME: Maybe need to fixup position?
        if (lhs != null) {
            return new OpAsgnConstDeclNode(line, lhs, symbolID(operatorName), rhs);
        } else {
            return new BeginNode(line, NilImplicitNode.NIL);
        }
    }

    public Node new_bodystmt(Node head, RescueBodyNode rescue, Node rescueElse, Node ensure) {
        Node node = head;

        if (rescue != null) {
            node = new RescueNode(getPosition(head), head, rescue, rescueElse);
        } else if (rescueElse != null) {
            // FIXME: MRI removed this...
            warn(lexer.tokline, "else without rescue is useless");
            node = appendToBlock(head, rescue);
        }
        if (ensure != null) {
            if (node != null) {
                node = new EnsureNode(getPosition(head), makeNullNil(node), ensure);
            } else {
                node = appendToBlock(ensure, NilImplicitNode.NIL);
            }
        }

        fixpos(node, head);
        return node;
    }

    public RubySymbol symbolID(ByteList identifierValue) {
        // FIXME: We walk this during identifier construction so we should calculate CR without having to walk twice.
        if (RubyString.scanForCodeRange(identifierValue) == StringSupport.CR_BROKEN) {
            Ruby runtime = getRuntime();
            throw runtime.newSyntaxError(str(runtime, "invalid symbol in encoding " + lexer.getEncoding() + " :\"", inspectIdentifierByteList(runtime, identifierValue), "\""));
        }

        return RubySymbol.newIDSymbol(getRuntime(), identifierValue);
    }

    public boolean isLazy(String callType) {
        return "&.".equals(callType);
    }

    public boolean isLazy(ByteList callType) {
        return callType == AMPERSAND_DOT;
    }
    
    public Node new_attrassign(int line, Node receiver, ByteList name, Node argsNode, boolean isLazy) {
        // We extract BlockPass from tree and insert it as a block node value (MRI wraps it around the args)
        Node blockNode = null;
        if (argsNode instanceof BlockPassNode) {
            blockNode = argsNode; // It is weird to leave this as-is but we need to know it vs iternode vs weird ast bug.
            argsNode = ((BlockPassNode) argsNode).getArgsNode();
        }

        return new AttrAssignNode(line, receiver, symbolID(name), argsNode, blockNode, isLazy);
    }

    public Node new_call(Node receiver, ByteList callType, ByteList name, Node argsNode, Node iter) {
        return new_call(receiver, callType, name, argsNode, iter, position(receiver, argsNode));
    }

    public Node new_call(Node receiver, ByteList callType, ByteList name, Node argsNode, Node iter, int line) {
        if (argsNode instanceof BlockPassNode) {
            if (iter != null) lexer.compile_error("both block arg and actual block given.");

            BlockPassNode blockPass = (BlockPassNode) argsNode;
            return new CallNode(line, receiver, symbolID(name), blockPass.getArgsNode(), blockPass, isLazy(callType));
        }

        return new CallNode(line, receiver, symbolID(name), argsNode, iter, isLazy(callType));
    }

    public Node new_call(Node receiver, ByteList name, Node argsNode, Node iter) {
        return new_call(receiver, DOT, name, argsNode, iter);
    }

    public Colon2Node new_colon2(int line, Node leftNode, ByteList name) {
        if (leftNode == null) return new Colon2ImplicitNode(line, symbolID(name));

        return new Colon2ConstNode(line, leftNode, symbolID(name));
    }

    public Colon3Node new_colon3(int line, ByteList name) {
        return new Colon3Node(line, symbolID(name));
    }

    public void frobnicate_fcall_args(FCallNode fcall, Node args, Node iter) {
        if (args instanceof BlockPassNode) {
            if (iter != null) lexer.compile_error("both block arg and actual block given.");

            BlockPassNode blockPass = (BlockPassNode) args;
            args = blockPass.getArgsNode();
            iter = blockPass;
        }

        fcall.setArgsNode(args);
        fcall.setIterNode(iter);
    }

    public void fixpos(Node node, Node orig) {
        if (node == null || orig == null) return;

        node.setLine(orig.getLine());
    }

    public Node new_fcall(ByteList operation) {
        return new FCallNode(lexer.tokline, symbolID(operation));
    }

    public Node new_super(int line, Node args) {
        if (args instanceof BlockPassNode) {
            return new SuperNode(line, ((BlockPassNode) args).getArgsNode(), args);
        }
        return new SuperNode(line, args);
    }

    /**
    *  Description of the RubyMethod
    */
    public void initTopLocalVariables() {
        currentScope = getTopStaticScope(lexer.getFile());
        scopedParserState = new ScopedParserState(null);
        warnOnUnusedVariables = getWarnings().isVerbose() && !isEval() && !isInline();
    }

    boolean isEval() {
        return type == ParserType.EVAL;
    }

    public void finalizeDynamicScope() {
        getResult().setScope(finalizeDynamicScope(currentScope));
    }
    /**
     * Gets the result.
     * @return Returns a RubyParserResult
     */
    public RubyParserResult getResult() {
        return result;
    }

    public DStrNode createDStrNode(int line) {
        return new DStrNode(line, lexer.getEncoding());
    }

    public KeyValuePair<Node, Node> createKeyValue(Node key, Node value) {
        if (key instanceof StrNode) ((StrNode) key).setFrozen(true);

        return new KeyValuePair<>(key, value);
    }

    public Node asSymbol(int line, ByteList value) {
        return new SymbolNode(line, symbolID(value));
    }

        
    public Node asSymbol(int line, Node value) {
        return value instanceof StrNode ? new SymbolNode(line, symbolID(((StrNode) value).getValue())) :
                new DSymbolNode(line, (DStrNode) value);
    }
    
    public Node literal_concat(Node head, Node tail) {
        if (head == null) return tail;
        if (tail == null) return head;
        
        if (head instanceof EvStrNode) {
            head = createDStrNode(head.getLine()).add(head);
        }

        if (lexer.getHeredocIndent() > 0) {
            if (head instanceof StrNode) {
                head = createDStrNode(head.getLine()).add(head);
                return list_append(head, tail);
            } else if (head instanceof DStrNode) {
                return list_append(head, tail);
            }
        }

        if (tail instanceof StrNode) {
            if (head instanceof StrNode) {
                StrNode front = (StrNode) head;
                // string_contents always makes an empty strnode...which is sometimes valid but
                // never if it ever is in literal_concat.
                if (front.getValue().getRealSize() > 0) {
                    return new StrNode(head.getLine(), front, (StrNode) tail);
                } else {
                    return tail;
                }
            } 
            head.setLine(head.getLine());
            return ((ListNode) head).add(tail);
        	
        } else if (tail instanceof DStrNode) {
            if (head instanceof StrNode) { // Str + oDStr -> Dstr(Str, oDStr.contents)
                DStrNode newDStr = new DStrNode(head.getLine(), ((DStrNode) tail).getEncoding());
                newDStr.add(head);
                newDStr.addAll(tail);
                return newDStr;
            } 

            return ((ListNode) head).addAll(tail);
        } 

        // tail must be EvStrNode at this point 
        if (head instanceof StrNode) {
        	
            //Do not add an empty string node
            if(((StrNode) head).getValue().length() == 0) {
                head = createDStrNode(head.getLine());
            } else {
                head = createDStrNode(head.getLine()).add(head);
            }
        }
        return ((DStrNode) head).add(tail);
    }

    public Node newRescueModNode(Node body, Node rescueBody) {
        if (rescueBody == null) rescueBody = NilImplicitNode.NIL; // foo rescue () can make null.
        int line = getPosition(body);
        body = remove_begin(body);
        rescueBody = remove_begin(rescueBody);

        if (body instanceof OpElementAsgnNode) {
            OpElementAsgnNode original = (OpElementAsgnNode) body;
            return new OpElementAsgnNode(line, original.getReceiverNode(), original.getOperatorSymbolName(),
                    original.getArgsNode(), new RescueModNode(line, original.getValueNode(), new RescueBodyNode(line, null, rescueBody, null)), original.getBlockNode());
        }

        return new RescueModNode(line, body, new RescueBodyNode(line, null, rescueBody, null));
    }
    
    public Node newEvStrNode(int line, Node node) {
        if (node instanceof StrNode || node instanceof EvStrNode) return node;

        return new EvStrNode(line, node);
    }
    
    public Node new_yield(int line, Node node) {
        if (node instanceof BlockPassNode) lexer.compile_error("Block argument should not be given.");

        return new YieldNode(line, node);
    }
    
    public NumericNode negateInteger(NumericNode integerNode) {
        if (integerNode instanceof FixnumNode) {
            FixnumNode fixnumNode = (FixnumNode) integerNode;
            
            fixnumNode.setValue(-fixnumNode.getValue());
            return fixnumNode;
        } else if (integerNode instanceof BignumNode) {
            BignumNode bignumNode = (BignumNode) integerNode;

            BigInteger value = bignumNode.getValue().negate();

            // Negating a bignum will make the last negative value of our bignum
            if (value.compareTo(RubyBignum.LONG_MIN) >= 0) {
                return new FixnumNode(bignumNode.getLine(), value.longValue());
            }
            
            bignumNode.setValue(value);
        }
        
        return integerNode;
    }
    
    public FloatNode negateFloat(FloatNode floatNode) {
        floatNode.setValue(-floatNode.getValue());
        
        return floatNode;
    }

    public ComplexNode negateComplexNode(ComplexNode complexNode) {
        complexNode.setNumber(negateNumeric(complexNode.getNumber()));

        return complexNode;
    }

    public RationalNode negateRational(RationalNode rationalNode) {
        return (RationalNode) rationalNode.negate();
    }
    
    private Node checkForNilNode(Node node, int defaultPosition) {
        return (node == null) ? new NilNode(defaultPosition) : node; 
    }

    public ArgsNode new_args(int line, ListNode pre, ListNode optional, RestArgNode rest,
            ListNode post, ArgsTailHolder tail) {
        ArgsNode argsNode;
        if (tail == null) {
            argsNode = new ArgsNode(line, pre, optional, rest, post, null);
        } else {
            if (tail.getBlockArg() instanceof ForwardingBlockArgNode) {
                if (rest != null) {
                    yyerror("... after rest argument");
                    argsNode = new ArgsNode(line, null, null, null, null,
                            tail.getKeywordArgs(), tail.getKeywordRestArgNode(), tail.getBlockArg());

                    getCurrentScope().setSignature(Signature.from(argsNode));

                    return argsNode;
                }
                int slot = getCurrentScope().addVariableThisScope(FWD_REST.toString());
                rest = new UnnamedRestArgNode(line, symbolID(FWD_REST), slot);
            }

            argsNode = new ArgsNode(line, pre, optional, rest, post,
                    tail.getKeywordArgs(), tail.getKeywordRestArgNode(), tail.getBlockArg());
        }

        getCurrentScope().setSignature(Signature.from(argsNode));

        return argsNode;
    }

    public ArgsTailHolder new_args_tail(int line, ListNode keywordArg,
                                        ByteList keywordRestArgName, BlockArgNode blockArg) {
        if (keywordRestArgName == null) return new ArgsTailHolder(line, keywordArg, null, blockArg);

        RubySymbol restKwargsName = symbolID(keywordRestArgName);
        String id = restKwargsName.idString();

        int slot = currentScope.exists(id);
        if (slot == -1) slot = currentScope.addVariable(id);

        KeywordRestArgNode keywordRestArg = new KeywordRestArgNode(line, restKwargsName, slot);

        return new ArgsTailHolder(line, keywordArg, keywordRestArg, blockArg);
    }

    protected ArgsTailHolder new_args_tail(int line, ListNode keywordArg,
                                           ByteList keywordRestArgName, ByteList block) {
        BlockArgNode blockArg = null;
        if (block != null) {
            ArgumentNode var = arg_var(block);

            blockArg = block == FWD_BLOCK ? new ForwardingBlockArgNode(var) : new BlockArgNode(var);
        }

        return new_args_tail(line, keywordArg, keywordRestArgName, blockArg);
    }

    public Node remove_duplicate_keys(final HashNode hash) {
        final Map<Node, KeyValuePair<Node, Node>> encounteredKeys = new HashMap<>();

        for (KeyValuePair<Node,Node> pair: hash.getPairs()) {
            final Node key = pair.getKey();
            if (!(key instanceof LiteralValue)) continue;
            if (encounteredKeys.containsKey(key)) {
                Ruby runtime = getRuntime();
                IRubyObject value = ((LiteralValue) key).literalValue(runtime);
                warning(ID.AMBIGUOUS_ARGUMENT, lexer.getFile(), hash.getLine(), str(runtime, "key ", value.inspect(),
                        " is duplicated and overwritten on line " + (key.getLine() + 1)));
            }
            // even if the key was previously seen, we replace the value to properly remove multiple duplicates
            encounteredKeys.put(key, pair);
        }

        // NOTE: we do not really remove the value part (RHS) as in that case we should evaluate the code - despite
        // the value being dropped the side effects are desired and something MRI evaluates explicitly during removal
        // with JRuby the modification of the hash should be done in the IR and not here (during the parsing phase)...

        return hash;
    }

    public static Node newAlias(int line, Node newNode, Node oldNode) {
        return new AliasNode(line, newNode, oldNode);
    }

    public static Node newUndef(int line, Node nameNode) {
        return new UndefNode(line, nameNode);
    }

    /**
     * generate parsing error
     */
    public void yyerror(String message) {
        lexer.compile_error(message);
    }

    public void yyerror(String message, ProductionState state) {
        lexer.compile_error(message, state.start, state.end);
    }

    /**
     * generate parsing error
     * @param message text to be displayed.
     * @param expected list of acceptable tokens, if available.
     */
    public void yyerror(String message, String[] expected, String found) {
        lexer.compile_error(message + ", unexpected " + found + "\n");
    }

    public int getPosition(Node start) {
        return start != null ? start.getLine() : lexer.getRubySourceline();
    }

    public void warn(String message) {
        warn(src_line(), message);
    }

    public void warn(int line, String message) {
        getWarnings().warn(ID.USELESS_EXPRESSION, lexer.getFile(), line + 1, message); // node/lexer lines are 0 based
    }

    // FIXME: Replace this with file/line version and stop using ISourcePosition
    public void warning(int line, String message) {
        warning(ID.USELESS_EXPRESSION, lexer.getFile(), line, message);
    }

    public void warning(ID id, String file, int line, String message) {
        getWarnings().warn(id, file, line + 1, message); // node/lexer lines are 0 based
    }

    // ENEBO: Totally weird naming (in MRI is not allocated and is a local var name) [1.9]
    public static boolean is_local_id(ByteList name) {
        return RubyLexer.isIdentifierChar(name.charAt(0));
    }

    @Deprecated
    public boolean is_local_id(String name) {
        return RubyLexer.isIdentifierChar(name.charAt(0));
    }

    // 1.9
    public ListNode list_append(Node list, Node item) {
        if (list == null) return new ArrayNode(item.getLine(), item);
        if (!(list instanceof ListNode)) return new ArrayNode(list.getLine(), list).add(item);

        return ((ListNode) list).add(item);
    }

    public Node new_bv(ByteList identifier) {
        if (!is_local_id(identifier)) getterIdentifierError(symbolID(identifier));

        shadowing_lvar(identifier);
        
        return arg_var(identifier);
    }

    // FIXME:
    public ArgumentNode arg_var(RubySymbol name) {
        return arg_var(name.getBytes());
    }

    public ArgumentNode arg_var(ByteList byteName) {
        // FIXME: parser is sending some keyword args as 'a:' instead of 'a' and since this is illegal we are
        //  working around it here.  Long term fix is to audit and figure out where this is happening and correct
        //  it.  Prism is replacing this parser so this felt like a lot less work.
        int length = byteName.length();
        if (length > 0 && byteName.get(length - 1) == ':') byteName.setRealSize(length - 1);
        RubySymbol name = symbolID(byteName);
        numparam_name(byteName);

        if (warnOnUnusedVariables) {
            scopedParserState.addDefinedVariable(name, lexer.getRubySourceline());
            scopedParserState.markUsedVariable(name, 0);
        }
        return new ArgumentNode(lexer.getRubySourceline(), name, getCurrentScope().addVariableThisScope(name.idString()));
    }

    public ByteList formal_argument(ByteList identifier, Object _unused) {
        lexer.validateFormalIdentifier(identifier);

        return shadowing_lvar(identifier);
    }

    public enum IDType {
        Local, Global, Instance, AttrSet, Constant, Class;
    }

    public static IDType id_type(ByteList identifier) {
        char first = identifier.charAt(0);

        if (Character.isUpperCase(first)) return Constant;

        switch(first) {
            case '@':
                return identifier.charAt(1) == '@' ? Class : Instance;
            case '$':
                return Global;
        }

        byte last = (byte) identifier.get(identifier.length() - 1);
        if (last == '=') {
            return AttrSet;
        }

        return Local;
    }

    public static boolean is_private_local_id(ByteList name) {
        if (name.realSize() == 1 && name.charAt(0) == '_') return true;
        if (!is_local_id(name)) return false;

        return name.charAt(0) == '_';
    }

    // 1.9
    public ByteList shadowing_lvar(ByteList nameBytes) {
        if (is_private_local_id(nameBytes)) return nameBytes;

        RubySymbol name = symbolID(nameBytes);
        String id = name.idString();

        StaticScope current = getCurrentScope();
        if (current.exists(id) >= 0) yyerror("duplicated argument name");

        if (warnOnUnusedVariables) {
            int slot = current.isDefined(id);
            if (slot != -1) {
                scopedParserState.addDefinedVariable(name, lexer.getRubySourceline());
                scopedParserState.markUsedVariable(name, slot >> 16);
            }
        }

        return nameBytes;
    }

    // 1.9
    public ListNode list_concat(Node first, Node second) {
        if (first instanceof ListNode) {
            if (second instanceof ListNode) {
                return ((ListNode) first).addAll((ListNode) second);
            } else {
                return ((ListNode) first).addAll(second);
            }
        }

        return new ArrayNode(first.getLine(), first).add(second);
    }

    // 1.9
    /**
     * If node is a splat and it is splatting a literal array then return the literal array.
     * Otherwise return null.  This allows grammar to not splat into a Ruby Array if splatting
     * a literal array.
     */
    public Node splat_array(Node node) {
        if (node instanceof SplatNode) node = ((SplatNode) node).getValue();
        if (node instanceof ArrayNode) return node;
        return null;
    }

    public Node arg_append(Node node1, Node node2) {
        if (node1 == null) return new ArrayNode(node2.getLine(), node2);
        if (node1 instanceof ListNode) return ((ListNode) node1).add(node2);
        if (node1 instanceof BlockPassNode) return arg_append(((BlockPassNode) node1).getBodyNode(), node2);
        if (node1 instanceof ArgsPushNode) {
            ArgsPushNode pushNode = (ArgsPushNode) node1;
            Node body = pushNode.getSecondNode();

            return new ArgsCatNode(pushNode.getLine(), pushNode.getFirstNode(),
                    new ArrayNode(body.getLine(), body).add(node2));
        }
        if (node1 instanceof ArgsCatNode) {
            ArgsCatNode pushNode = (ArgsCatNode) node1;
            Node body = pushNode.getSecondNode();
            if (body instanceof ListNode) {
                ((ListNode) body).add(node2);
                return node1;
            }
        }
        return new ArgsPushNode(position(node1, node2), node1, node2);
    }

    private List<Integer> allocateNamedLocals(RegexpNode regexpNode) {
        RubyRegexp pattern = RubyRegexp.newRegexp(getRuntime(), regexpNode.getValue(), regexpNode.getOptions());
        pattern.setLiteral();
        String[] names = pattern.getNames();
        List<Integer> locals = new ArrayList<>();
        StaticScope scope = getCurrentScope();

        Ruby runtime = getRuntime();
        for (String name : names) {
            if (RubyLexer.getKeyword(name) == null && !Character.isUpperCase(name.charAt(0))) {
                String id = runtime.newSymbol(name).idString();
                int slot = scope.isDefined(id);
                if (slot >= 0) {
                    locals.add(slot);
                } else {
                    int index = getCurrentScope().addVariableThisScope(id);
                    locals.add(index);
                    scopedParserState.growNamedCaptures(index);
                }
            }
        }

        return locals;
    }

    public void compile_error(String message) { // mri: rb_compile_error_with_enc
        String line = lexer.getCurrentLine();
        int pos = lexer.getRubySourceline();
        String errorMessage = lexer.getFile() + ":" + (pos + 1) + ": ";

        if (line != null && line.length() > 5) {
            boolean addNewline = message != null && ! message.endsWith("\n");

            message += (addNewline ? "\n" : "") + line;
        }

        throw getRuntime().newSyntaxError(errorMessage + message);
    }

    public Node new_regexp(int line, Node contents, RegexpNode end) {
        Ruby runtime = getRuntime();
        RegexpOptions options = end.getOptions();
        Encoding encoding = lexer.getEncoding();

        if (contents == null) {
            ByteList newValue = ByteList.create("");
            if (encoding != null) {
                newValue.setEncoding(encoding);
            }

            lexer.checkRegexpFragment(runtime, newValue, options);
            return new RegexpNode(line, newValue, options.withoutOnce());
        } else if (contents instanceof StrNode) {
            ByteList meat = (ByteList) ((StrNode) contents).getValue().clone();
            lexer.checkRegexpFragment(runtime, meat, options);
            lexer.checkRegexpSyntax(runtime, meat, options.withoutOnce());
            return new RegexpNode(contents.getLine(), meat, options.withoutOnce());
        } else if (contents instanceof DStrNode) {
            DStrNode dStrNode = (DStrNode) contents;
            
            for (int i = 0; i < dStrNode.size(); i++) {
                Node fragment = dStrNode.get(i);
                if (fragment instanceof StrNode) {
                    ByteList frag = ((StrNode) fragment).getValue();
                    lexer.checkRegexpFragment(runtime, frag, options);
//                    if (!lexer.isOneEight()) encoding = frag.getEncoding();
                }
            }
            
            DRegexpNode dRegexpNode = new DRegexpNode(line, options, encoding);
            dRegexpNode.add(new StrNode(contents.getLine(), createMaster(options)));
            dRegexpNode.addAll(dStrNode);
            return dRegexpNode;
        }

        // EvStrNode: #{val}: no fragment check, but at least set encoding
        ByteList master = createMaster(options);
        lexer.checkRegexpFragment(runtime, master, options);
        encoding = master.getEncoding();
        DRegexpNode node = new DRegexpNode(line, options, encoding);
        node.add(new StrNode(contents.getLine(), master));
        node.add(contents);
        return node;
    }
    
    // Create the magical empty 'master' string which will be encoded with
    // regexp options encoding so dregexps can end up starting with the
    // right encoding.
    private ByteList createMaster(RegexpOptions options) {
        Encoding encoding = options.setup(getRuntime());

        return new ByteList(ByteList.NULL_ARRAY, encoding);
    }
    
    // FIXME:  This logic is used by many methods in MRI, but we are only using it in lexer
    // currently.  Consolidate this when we tackle a big encoding refactoring
    public static int associateEncoding(ByteList buffer, Encoding newEncoding, int codeRange) {
        Encoding bufferEncoding = buffer.getEncoding();
                
        if (newEncoding == bufferEncoding) return codeRange;
        
        // TODO: Special const error
        
        buffer.setEncoding(newEncoding);
        
        if (codeRange != StringSupport.CR_7BIT || !newEncoding.isAsciiCompatible()) {
            return StringSupport.CR_UNKNOWN;
        }
        
        return codeRange;
    }
    
    public NumericNode negateNumeric(NumericNode node) {
        switch (node.getNodeType()) {
            case FIXNUMNODE:
            case BIGNUMNODE:
                return negateInteger(node);
            case COMPLEXNODE:
                return negateComplexNode((ComplexNode) node);
            case FLOATNODE:
                return negateFloat((FloatNode) node);
            case RATIONALNODE:
                return negateRational((RationalNode) node);
        }
        
        yyerror("Invalid or unimplemented numeric to negate: " + node.toString());
        return null;
    }

    public static final ByteList INTERNAL_ID = new ByteList(new byte[] {}, USASCIIEncoding.INSTANCE);

    @Deprecated
    public String internalId() {
        return INTERNAL_ID.toString();
    }

    public Set<ByteList> push_pvtbl() {
        Set<ByteList> currentTable = variableTable;

        variableTable = new HashSet<>();

        return currentTable;
    }

    public void pop_pvtbl(Set<ByteList> table) {
        variableTable = table;
    }

    public Set<ByteList> push_pktbl() {
        Set<ByteList> currentTable = keyTable;

        keyTable = new HashSet<>();

        return currentTable;
    }

    public void pop_pktbl(Set<ByteList> table) {
        keyTable = table;
    }

    public Node newIn(int line, Node expression, Node body, Node nextCase) {
        return new InNode(line, expression, body, nextCase);
    }

    public void endless_method_name(DefHolder name) {
        // FIXME: IMPL
    }

    public Node reduce_nodes(Node body) {
        // FIXME: impl
        return body;
    }

    public void restore_defun(DefHolder holder) {
        lexer.getLexContext().restore(holder);
        lexer.setCurrentArg(holder.current_arg);
    }

    public ArrayPatternNode new_array_pattern(int line, Node constant, Node preArg, ArrayPatternNode arrayPattern) {
        arrayPattern.setConstant(constant);

        if (preArg != null) {
            ListNode preArgs = new ListNode(line, preArg);
            ListNode arrayPatternPreArgs = arrayPattern.getPreArgs();

            arrayPattern.setPreArgs(arrayPatternPreArgs != null ?
                    list_concat(preArgs, arrayPatternPreArgs) :
                    preArgs);
        }

        return arrayPattern;
    }

    public HashPatternNode new_hash_pattern(Node constant, HashPatternNode hashPatternNode) {
        hashPatternNode.setConstant(constant);

        return hashPatternNode;
    }

    public static ByteList NIL = new ByteList(new byte[] {'n', 'i', 'l'});

    public HashNode none() {
        return null;
    }

    public HashPatternNode new_hash_pattern_tail(int line, HashNode keywordArgs, ByteList keywordRestArg) {
        Node restArg;

        if (keywordRestArg == KWNOREST) {          // '**nil'
            restArg = new NilRestArgNode(line);
        } else if (keywordRestArg == STAR_STAR) { // '**' (MRI uses null but something wrong and this is more explicit)
            restArg = new StarNode(lexer.getRubySourceline());
        } else if (keywordRestArg != null) {       // '**something'
            restArg = assignableLabelOrIdentifier(keywordRestArg, null);
        } else {
            restArg = null;
        }

        return new HashPatternNode(line, restArg, keywordArgs == null ? new HashNode(line) : keywordArgs);
    }

    public void warn_experimental(int line, String message) {
        ((RubyWarnings) getWarnings()).warnExperimental(lexer.getFile(), line, message);
    }

    public Node rescued_expr(int line, Node arg, Node rescue) {
        return new RescueNode(line, arg,
                new RescueBodyNode(line, null, remove_begin(rescue), null), null);
    }

    public ArrayPatternNode new_array_pattern_tail(int line, ListNode preArgs, boolean hasRest, ByteList restArg, ListNode postArgs) {
        return new ArrayPatternNode(
                line,
                preArgs,
                hasRest ?
                        restArg != null ?
                                assignableLabelOrIdentifier(restArg, null) :
                                new StarNode(lexer.getRubySourceline()) :
                        null,
                postArgs);
    }

    public void error_duplicate_pattern_key(ByteList key) {
        // This is for bare one-line matches ({a: 1} => a:).
        if (keyTable == null) keyTable = new HashSet<>();
        if (keyTable.contains(key)) yyerror("duplicated key name");

        keyTable.add(key);
    }

    public void error_duplicate_pattern_variable(ByteList variable) {
        if (is_private_local_id(variable)) return;
        if (variableTable.contains(variable)) yyerror("duplicated variable name");

        variableTable.add(variable);
    }

    public Node new_find_pattern(Node constant, FindPatternNode findPattern) {
        findPattern.setConstant(constant);

        return findPattern;
    }

    public Node new_find_pattern_tail(int line, ByteList preRestArg, ListNode postArgs, ByteList postRestArg) {
        // FIXME: in MRI all the StarNodes are the same node and so perhaps source line for them is unimportant.
        return new FindPatternNode(
                line,
                preRestArg != null ? assignableLabelOrIdentifier(preRestArg, null) :  new StarNode(lexer.getRubySourceline()),
                postArgs,
                postRestArg != null ? assignableLabelOrIdentifier(postRestArg, null) :  new StarNode(lexer.getRubySourceline()));
    }

    public boolean local_id(ByteList value) {
        // FIXME: local_id_ref is more complicated and we just blanket look for a scope var of the same name.
        return currentScope.isDefined(symbolID(value).idString()) >= 0;
    }

    public boolean check_forwarding_args() {
        if (local_id(FWD_ALL)) return true;
        compile_error("unexpected ...");
        return false;
    }

    public void add_forwarding_args() {
        arg_var(FWD_REST);
        arg_var(FWD_KWREST);
        arg_var(FWD_BLOCK);
        arg_var(FWD_ALL);  // Add dummy value to make it easy to see later that is ...
    }

    public Node new_args_forward_call(int line, Node leadingArgs) {
        RubySymbol splatName = symbolID(FWD_REST);
        int splatLoc = getCurrentScope().isDefined(splatName.idString());
        Node splatNode = new SplatNode(line, new LocalVarNode(line, splatLoc, splatName));
        RubySymbol kwRestName = symbolID(FWD_KWREST);
        int kwRestLoc = getCurrentScope().isDefined(kwRestName.idString());
        Node restNode = new LocalVarNode(line, kwRestLoc, kwRestName);
        RubySymbol blockName = symbolID(FWD_BLOCK);
        int blockLoc = getCurrentScope().isDefined(blockName.idString());
        BlockPassNode block = new BlockPassNode(line, new LocalVarNode(line, blockLoc, blockName));
        Node args = leadingArgs != null ? rest_arg_append(leadingArgs, splatNode) : splatNode;
        args = arg_append(args, new HashNode(line, new KeyValuePair<>(null, restNode)));
        return arg_blk_pass(args, block);
    }

    public void check_literal_when(Node one) {
        // FIXME: IMPL
    }

    public Node last_arg_append(Node args, Node lastArg) {
        Node n1 = splat_array(args);

        return n1 == null ?  arg_append(args, lastArg) : list_append(n1, lastArg);
    }

    public Node rest_arg_append(Node args, Node restArg) {
        Node n1;
        if ((restArg instanceof ListNode) && (n1 = splat_array(args)) != null) {
            return list_concat(n1, restArg);
        }
        return arg_concat(args, restArg);
    }

    public Node remove_begin(Node node) {
        while (node instanceof BeginNode) {
            Node body = ((BeginNode) node).getBodyNode();
            if (body == null) break;
            node = body;
        }

        return node;
    }

    public void nd_set_first_loc(Node node, int line) {
        // FIXME: IMPL
    }

    public RubyParserResult parse() throws IOException {
        yyparse(lexer, runtime.getInstanceConfig().isDebug() ? new YYDebug() : null);

        return result;
    }

    protected abstract Object yyparse(RubyLexer lexer, Object yyDebug) throws IOException;

    protected LexContext getLexContext() {
        return lexer.getLexContext();
    }

    protected int src_line() {
        return lexer.getRubySourceline();
    }

    protected int getHeredocIndent() {
        return lexer.getHeredocIndent();
    }

    protected void setHeredocIndent(int value) {
        lexer.setHeredocIndent(value);
    }

    protected int getBraceNest() {
        return lexer.getBraceNest();
    }

    protected void setBraceNest(int value) {
        lexer.setBraceNest(value);
    }

    protected int getState() {
        return lexer.getState();
    }

    protected void setState(int value) {
        lexer.setState(value);
    }

    protected Encoding getEncoding() {
        return lexer.getEncoding();
    }

    protected void setCommandStart(boolean value) {
        lexer.commandStart = value;
    }

    protected ByteList getCurrentArg() {
        return lexer.getCurrentArg();
    }

    protected void setCurrentArg(RubySymbol value) {
        lexer.setCurrentArg(value == null ?  null : value.getBytes());
    }

    protected StrNode createStr(ByteList buffer, int flags) {
        return lexer.createStr(buffer, flags);
    }

    protected StackState getCmdArgumentState() {
        return lexer.getCmdArgumentState();
    }

    protected StackState getConditionState() {
        return lexer.getConditionState();
    }

    protected int getLeftParenBegin() {
        return lexer.getLeftParenBegin();
    }

    protected int getParenNest() {
        return lexer.getParenNest();
    }

    protected ByteList extractByteList(Object value) {
        if (value instanceof ByteList) return (ByteList) value;
        if (value instanceof RubyString) return ((RubyString) value).getByteList();
        if (value instanceof RubySymbol) return ((RubySymbol) value).getBytes();

        throw new RuntimeException("Got unexpected object: " + value);
    }

    protected void setLeftParenBegin(int value) {
        lexer.setLeftParenBegin(value);
    }

    protected String getFile() {
        return lexer.getFile();
    }

    protected void heredoc_dedent(Node node) {
        lexer.heredoc_dedent(node);
    }

    protected StrTerm getStrTerm() {
        return lexer.getStrTerm();
    }

    protected void setStrTerm(StrTerm value) {
        lexer.setStrTerm(value);
    }

    protected void setHeredocLineIndent(int indent) {
        lexer.setHeredocLineIndent(indent);
    }

    public Ruby getRuntime() {
        return runtime;
    }

    public Node nil() {
        return NilImplicitNode.NIL;
    }

    public RubySymbol get_id(ByteList id) {
        return symbolID(id);
    }

    public IRubyWarnings getWarnings() {
        return runtime.getWarnings();
    }

    public boolean isEndSeen() {
        return lexer.isEndSeen();
    }

    public boolean isFrozenStringLiteral() {
        return frozenStringLiterals;
    }

    public void setFrozenStringLiteral(boolean b) {
        frozenStringLiterals = b;
    }

    public DynamicScope finalizeDynamicScope(StaticScope staticScope) {
        // Eval scooped up some new variables changing the size of the scope.
        if (existingScope != null && (type != ParserType.NORMAL)) {
            existingScope.growIfNeeded();
            return existingScope;
        }

        return DynamicScope.newDynamicScope(staticScope, existingScope);
    }

    /**
     * Returns the static scope which represents the top of the parse.  If an eval
     * then we will have an existing scope to return.  If not then we make a new
     * one since we are starting from scratch.
     *
     * @param file to name top scope if we have a new scope
     * @return a static scope
     */
    public StaticScope getTopStaticScope(String file) {
        return existingScope != null ?
                existingScope.getStaticScope() :
                runtime.getStaticScopeFactory().newLocalScope(null, file);
    }

    public boolean isCoverageEnabled() {
        return !isEval() && getRuntime().getCoverageData().isCoverageEnabled();
    }

    /**
     * Zero out coverable lines as they're encountered
     */
    public void coverLine(int i) {
        // We had an overflow so we cannot mark whatever line this is as covered.
        if (i < 0) return;
        if (isCoverageEnabled()) {
            growCoverageLines(i);
            coverage[i] = 0;
        }
    }

    /**
     *  Called by coverLine to grow it large enough to add new covered line.
     *  Also called at end up parse to pick up any extra non-code lines which
     *  should be marked -1 for not valid code lines.
     */
    public void growCoverageLines(int i) {
        if (coverage == null) {
            coverage = new int[i + 1];
        } else if (coverage.length <= i) {
            int[] newCoverage = new int[i + 1];
            Arrays.fill(newCoverage, -1);
            System.arraycopy(coverage, 0, newCoverage, 0, coverage.length);
            coverage = newCoverage;
        }
    }

    /**
     * At end of a parse if coverage is enabled we will do final processing
     * of the primitive coverage array and make sure runtimes coverage data
     * has been updated with this new data.
     */
    public CoverageData finishCoverage(String file, int lines) {
        if (!isCoverageEnabled()) return null;

        growCoverageLines(lines);
        CoverageData data = runtime.getCoverageData();
        data.prepareCoverage(file, coverage);
        return data;
    }

    public static final ByteList NOT = BANG;
}
