/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.codegen;

import static jdk.nashorn.internal.codegen.CompilerConstants.EVAL;
import static jdk.nashorn.internal.codegen.CompilerConstants.RETURN;
import static jdk.nashorn.internal.ir.Expression.isAlwaysTrue;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
import java.util.regex.Pattern;
import jdk.nashorn.internal.ir.AccessNode;
import jdk.nashorn.internal.ir.BaseNode;
import jdk.nashorn.internal.ir.BinaryNode;
import jdk.nashorn.internal.ir.Block;
import jdk.nashorn.internal.ir.BlockLexicalContext;
import jdk.nashorn.internal.ir.BlockStatement;
import jdk.nashorn.internal.ir.BreakNode;
import jdk.nashorn.internal.ir.CallNode;
import jdk.nashorn.internal.ir.CaseNode;
import jdk.nashorn.internal.ir.CatchNode;
import jdk.nashorn.internal.ir.ClassNode;
import jdk.nashorn.internal.ir.ContinueNode;
import jdk.nashorn.internal.ir.DebuggerNode;
import jdk.nashorn.internal.ir.EmptyNode;
import jdk.nashorn.internal.ir.Expression;
import jdk.nashorn.internal.ir.ExpressionStatement;
import jdk.nashorn.internal.ir.ForNode;
import jdk.nashorn.internal.ir.FunctionNode;
import jdk.nashorn.internal.ir.IdentNode;
import jdk.nashorn.internal.ir.IfNode;
import jdk.nashorn.internal.ir.IndexNode;
import jdk.nashorn.internal.ir.JumpStatement;
import jdk.nashorn.internal.ir.JumpToInlinedFinally;
import jdk.nashorn.internal.ir.LabelNode;
import jdk.nashorn.internal.ir.LexicalContext;
import jdk.nashorn.internal.ir.LiteralNode;
import jdk.nashorn.internal.ir.LiteralNode.ArrayLiteralNode;
import jdk.nashorn.internal.ir.LiteralNode.PrimitiveLiteralNode;
import jdk.nashorn.internal.ir.LoopNode;
import jdk.nashorn.internal.ir.Node;
import jdk.nashorn.internal.ir.ObjectNode;
import jdk.nashorn.internal.ir.ReturnNode;
import jdk.nashorn.internal.ir.RuntimeNode;
import jdk.nashorn.internal.ir.Statement;
import jdk.nashorn.internal.ir.SwitchNode;
import jdk.nashorn.internal.ir.Symbol;
import jdk.nashorn.internal.ir.ThrowNode;
import jdk.nashorn.internal.ir.TryNode;
import jdk.nashorn.internal.ir.UnaryNode;
import jdk.nashorn.internal.ir.VarNode;
import jdk.nashorn.internal.ir.WhileNode;
import jdk.nashorn.internal.ir.WithNode;
import jdk.nashorn.internal.ir.visitor.NodeOperatorVisitor;
import jdk.nashorn.internal.ir.visitor.SimpleNodeVisitor;
import jdk.nashorn.internal.parser.Token;
import jdk.nashorn.internal.parser.TokenType;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.ECMAErrors;
import jdk.nashorn.internal.runtime.ErrorManager;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.Source;
import jdk.nashorn.internal.runtime.logging.DebugLogger;
import jdk.nashorn.internal.runtime.logging.Loggable;
import jdk.nashorn.internal.runtime.logging.Logger;

Lower to more primitive operations. After lowering, an AST still has no symbols
and types, but several nodes have been turned into more low level constructs
and control flow termination criteria have been computed.
We do things like code copying/inlining of finallies here, as it is much
harder and context dependent to do any code copying after symbols have been
finalized.
/**
 * Lower to more primitive operations. After lowering, an AST still has no symbols
 * and types, but several nodes have been turned into more low level constructs
 * and control flow termination criteria have been computed.
 *
 * We do things like code copying/inlining of finallies here, as it is much
 * harder and context dependent to do any code copying after symbols have been
 * finalized.
 */
@Logger(name="lower")
final class Lower extends NodeOperatorVisitor<BlockLexicalContext> implements Loggable {

    private final DebugLogger log;
    private final boolean es6;
    private final Source source;

    // Conservative pattern to test if element names consist of characters valid for identifiers.
    // This matches any non-zero length alphanumeric string including _ and $ and not starting with a digit.
    private static final Pattern SAFE_PROPERTY_NAME = Pattern.compile("[a-zA-Z_$][\\w$]*");

    
Constructor.
/**
     * Constructor.
     */
    Lower(final Compiler compiler) {
        super(new BlockLexicalContext() {

            @Override
            public List<Statement> popStatements() {
                final List<Statement> newStatements = new ArrayList<>();
                boolean terminated = false;

                final List<Statement> statements = super.popStatements();
                for (final Statement statement : statements) {
                    if (!terminated) {
                        newStatements.add(statement);
                        if (statement.isTerminal() || statement instanceof JumpStatement) { //TODO hasGoto? But some Loops are hasGoto too - why?
                            terminated = true;
                        }
                    } else {
                        FoldConstants.extractVarNodesFromDeadCode(statement, newStatements);
                    }
                }
                return newStatements;
            }

            @Override
            protected Block afterSetStatements(final Block block) {
                final List<Statement> stmts = block.getStatements();
                for(final ListIterator<Statement> li = stmts.listIterator(stmts.size()); li.hasPrevious();) {
                    final Statement stmt = li.previous();
                    // popStatements() guarantees that the only thing after a terminal statement are uninitialized
                    // VarNodes. We skip past those, and set the terminal state of the block to the value of the
                    // terminal state of the first statement that is not an uninitialized VarNode.
                    if(!(stmt instanceof VarNode && ((VarNode)stmt).getInit() == null)) {
                        return block.setIsTerminal(this, stmt.isTerminal());
                    }
                }
                return block.setIsTerminal(this, false);
            }
        });

        this.log = initLogger(compiler.getContext());
        this.es6 = compiler.getScriptEnvironment()._es6;
        this.source = compiler.getSource();
    }

    @Override
    public DebugLogger getLogger() {
        return log;
    }

    @Override
    public DebugLogger initLogger(final Context context) {
        return context.getLogger(this.getClass());
    }

    @Override
    public boolean enterBreakNode(final BreakNode breakNode) {
        addStatement(breakNode);
        return false;
    }

    @Override
    public Node leaveCallNode(final CallNode callNode) {
        return checkEval(callNode.setFunction(markerFunction(callNode.getFunction())));
    }

    @Override
    public boolean enterCatchNode(final CatchNode catchNode) {
        Expression exception = catchNode.getException();
        if ((exception != null) && !(exception instanceof IdentNode)) {
            throwNotImplementedYet("es6.destructuring", exception);
        }
        return true;
    }

    @Override
    public Node leaveCatchNode(final CatchNode catchNode) {
        return addStatement(catchNode);
    }

    @Override
    public boolean enterContinueNode(final ContinueNode continueNode) {
        addStatement(continueNode);
        return false;
    }

    @Override
    public boolean enterDebuggerNode(final DebuggerNode debuggerNode) {
        final int line = debuggerNode.getLineNumber();
        final long token = debuggerNode.getToken();
        final int finish = debuggerNode.getFinish();
        addStatement(new ExpressionStatement(line, token, finish, new RuntimeNode(token, finish, RuntimeNode.Request.DEBUGGER, new ArrayList<Expression>())));
        return false;
    }

    @Override
    public boolean enterJumpToInlinedFinally(final JumpToInlinedFinally jumpToInlinedFinally) {
        addStatement(jumpToInlinedFinally);
        return false;
    }

    @Override
    public boolean enterEmptyNode(final EmptyNode emptyNode) {
        return false;
    }

    @Override
    public Node leaveIndexNode(final IndexNode indexNode) {
        final String name = getConstantPropertyName(indexNode.getIndex());
        if (name != null) {
            // If index node is a constant property name convert index node to access node.
            assert indexNode.isIndex();
            return new AccessNode(indexNode.getToken(), indexNode.getFinish(), indexNode.getBase(), name);
        }
        return super.leaveIndexNode(indexNode);
    }

    // If expression is a primitive literal that is not an array index and does return its string value. Else return null.
    private static String getConstantPropertyName(final Expression expression) {
        if (expression instanceof LiteralNode.PrimitiveLiteralNode) {
            final Object value = ((LiteralNode) expression).getValue();
            if (value instanceof String && SAFE_PROPERTY_NAME.matcher((String) value).matches()) {
                return (String) value;
            }
        }
        return null;
    }

    @Override
    public Node leaveExpressionStatement(final ExpressionStatement expressionStatement) {
        final Expression expr = expressionStatement.getExpression();
        ExpressionStatement node = expressionStatement;

        final FunctionNode currentFunction = lc.getCurrentFunction();

        if (currentFunction.isProgram()) {
            if (!isInternalExpression(expr) && !isEvalResultAssignment(expr)) {
                node = expressionStatement.setExpression(
                    new BinaryNode(
                        Token.recast(
                            expressionStatement.getToken(),
                            TokenType.ASSIGN),
                        compilerConstant(RETURN),
                    expr));
            }
        }

        if (es6 && expressionStatement.destructuringDeclarationType() != null) {
            throwNotImplementedYet("es6.destructuring", expressionStatement);
        }

        return addStatement(node);
    }

    @Override
    public Node leaveBlockStatement(final BlockStatement blockStatement) {
        return addStatement(blockStatement);
    }

    @Override
    public boolean enterForNode(final ForNode forNode) {
        if (es6 && (forNode.getInit() instanceof ObjectNode || forNode.getInit() instanceof ArrayLiteralNode)) {
            throwNotImplementedYet("es6.destructuring", forNode);
        }
        return super.enterForNode(forNode);
    }

    @Override
    public Node leaveForNode(final ForNode forNode) {
        ForNode newForNode = forNode;

        final Expression test = forNode.getTest();
        if (!forNode.isForInOrOf() && isAlwaysTrue(test)) {
            newForNode = forNode.setTest(lc, null);
        }

        newForNode = checkEscape(newForNode);
        if(!es6 && newForNode.isForInOrOf()) {
            // Wrap it in a block so its internally created iterator is restricted in scope, unless we are running
            // in ES6 mode, in which case the parser already created a block to capture let/const declarations.
            addStatementEnclosedInBlock(newForNode);
        } else {
            addStatement(newForNode);
        }
        return newForNode;
    }

    @Override
    public boolean enterFunctionNode(final FunctionNode functionNode) {
        if (es6) {
            if (functionNode.getKind() == FunctionNode.Kind.MODULE) {
                throwNotImplementedYet("es6.module", functionNode);
            }

            if (functionNode.getKind() == FunctionNode.Kind.GENERATOR) {
                throwNotImplementedYet("es6.generator", functionNode);
            }
            if (functionNode.usesSuper()) {
                throwNotImplementedYet("es6.super", functionNode);
            }

            final int numParams = functionNode.getNumOfParams();
            if (numParams > 0) {
                final IdentNode lastParam = functionNode.getParameter(numParams - 1);
                if (lastParam.isRestParameter()) {
                    throwNotImplementedYet("es6.rest.param", lastParam);
                }
            }
            for (final IdentNode param : functionNode.getParameters()) {
                if (param.isDestructuredParameter()) {
                    throwNotImplementedYet("es6.destructuring", functionNode);
                }
            }
        }

        return super.enterFunctionNode(functionNode);
    }

    @Override
    public Node leaveFunctionNode(final FunctionNode functionNode) {
        log.info("END FunctionNode: ", functionNode.getName());
        return functionNode;
    }

    @Override
    public Node leaveIfNode(final IfNode ifNode) {
        return addStatement(ifNode);
    }

    @Override
    public Node leaveIN(final BinaryNode binaryNode) {
        return new RuntimeNode(binaryNode);
    }

    @Override
    public Node leaveINSTANCEOF(final BinaryNode binaryNode) {
        return new RuntimeNode(binaryNode);
    }

    @Override
    public Node leaveLabelNode(final LabelNode labelNode) {
        return addStatement(labelNode);
    }

    @Override
    public Node leaveReturnNode(final ReturnNode returnNode) {
        addStatement(returnNode); //ReturnNodes are always terminal, marked as such in constructor
        return returnNode;
    }

    @Override
    public Node leaveCaseNode(final CaseNode caseNode) {
        // Try to represent the case test as an integer
        final Node test = caseNode.getTest();
        if (test instanceof LiteralNode) {
            final LiteralNode<?> lit = (LiteralNode<?>)test;
            if (lit.isNumeric() && !(lit.getValue() instanceof Integer)) {
                if (JSType.isRepresentableAsInt(lit.getNumber())) {
                    return caseNode.setTest((Expression)LiteralNode.newInstance(lit, lit.getInt32()).accept(this));
                }
            }
        }
        return caseNode;
    }

    @Override
    public Node leaveSwitchNode(final SwitchNode switchNode) {
        if(!switchNode.isUniqueInteger()) {
            // Wrap it in a block so its internally created tag is restricted in scope
            addStatementEnclosedInBlock(switchNode);
        } else {
            addStatement(switchNode);
        }
        return switchNode;
    }

    @Override
    public Node leaveThrowNode(final ThrowNode throwNode) {
        return addStatement(throwNode); //ThrowNodes are always terminal, marked as such in constructor
    }

    @SuppressWarnings("unchecked")
    private static <T extends Node> T ensureUniqueNamesIn(final T node) {
        return (T)node.accept(new SimpleNodeVisitor() {
            @Override
            public Node leaveFunctionNode(final FunctionNode functionNode) {
                final String name = functionNode.getName();
                return functionNode.setName(lc, lc.getCurrentFunction().uniqueName(name));
            }

            @Override
            public Node leaveDefault(final Node labelledNode) {
                return labelledNode.ensureUniqueLabels(lc);
            }
        });
    }

    private static Block createFinallyBlock(final Block finallyBody) {
        final List<Statement> newStatements = new ArrayList<>();
        for (final Statement statement : finallyBody.getStatements()) {
            newStatements.add(statement);
            if (statement.hasTerminalFlags()) {
                break;
            }
        }
        return finallyBody.setStatements(null, newStatements);
    }

    private Block catchAllBlock(final TryNode tryNode) {
        final int  lineNumber = tryNode.getLineNumber();
        final long token      = tryNode.getToken();
        final int  finish     = tryNode.getFinish();

        final IdentNode exception = new IdentNode(token, finish, lc.getCurrentFunction().uniqueName(CompilerConstants.EXCEPTION_PREFIX.symbolName()));

        final Block catchBody = new Block(token, finish, new ThrowNode(lineNumber, token, finish, new IdentNode(exception), true));
        assert catchBody.isTerminal(); //ends with throw, so terminal

        final CatchNode catchAllNode  = new CatchNode(lineNumber, token, finish, new IdentNode(exception), null, catchBody, true);
        final Block     catchAllBlock = new Block(token, finish, catchAllNode);

        //catchallblock -> catchallnode (catchnode) -> exception -> throw

        return (Block)catchAllBlock.accept(this); //not accepted. has to be accepted by lower
    }

    private IdentNode compilerConstant(final CompilerConstants cc) {
        final FunctionNode functionNode = lc.getCurrentFunction();
        return new IdentNode(functionNode.getToken(), functionNode.getFinish(), cc.symbolName());
    }

    private static boolean isTerminalFinally(final Block finallyBlock) {
        return finallyBlock.getLastStatement().hasTerminalFlags();
    }

    
Splice finally code into all endpoints of a trynode
Params:
tryNode – the try node
rethrow – the rethrowing throw nodes from the synthetic catch block
finallyBody – the code in the original finally block
Returns:
new try node after splicing finally code (same if nop)/**
     * Splice finally code into all endpoints of a trynode
     * @param tryNode the try node
     * @param rethrow the rethrowing throw nodes from the synthetic catch block
     * @param finallyBody the code in the original finally block
     * @return new try node after splicing finally code (same if nop)
     */
    private TryNode spliceFinally(final TryNode tryNode, final ThrowNode rethrow, final Block finallyBody) {
        assert tryNode.getFinallyBody() == null;

        final Block finallyBlock = createFinallyBlock(finallyBody);
        final ArrayList<Block> inlinedFinallies = new ArrayList<>();
        final FunctionNode fn = lc.getCurrentFunction();
        final TryNode newTryNode = (TryNode)tryNode.accept(new SimpleNodeVisitor() {

            @Override
            public boolean enterFunctionNode(final FunctionNode functionNode) {
                // do not enter function nodes - finally code should not be inlined into them
                return false;
            }

            @Override
            public Node leaveThrowNode(final ThrowNode throwNode) {
                if (rethrow == throwNode) {
                    return new BlockStatement(prependFinally(finallyBlock, throwNode));
                }
                return throwNode;
            }

            @Override
            public Node leaveBreakNode(final BreakNode breakNode) {
                return leaveJumpStatement(breakNode);
            }

            @Override
            public Node leaveContinueNode(final ContinueNode continueNode) {
                return leaveJumpStatement(continueNode);
            }

            private Node leaveJumpStatement(final JumpStatement jump) {
                // NOTE: leaveJumpToInlinedFinally deliberately does not delegate to this method, only break and
                // continue are edited. JTIF nodes should not be changed, rather the surroundings of
                // break/continue/return that were moved into the inlined finally block itself will be changed.

                // If this visitor's lc doesn't find the target of the jump, it means it's external to the try block.
                if (jump.getTarget(lc) == null) {
                    return createJumpToInlinedFinally(fn, inlinedFinallies, prependFinally(finallyBlock, jump));
                }
                return jump;
            }

            @Override
            public Node leaveReturnNode(final ReturnNode returnNode) {
                final Expression expr = returnNode.getExpression();
                if (isTerminalFinally(finallyBlock)) {
                    if (expr == null) {
                        // Terminal finally; no return expression.
                        return createJumpToInlinedFinally(fn, inlinedFinallies, ensureUniqueNamesIn(finallyBlock));
                    }
                    // Terminal finally; has a return expression.
                    final List<Statement> newStatements = new ArrayList<>(2);
                    final int retLineNumber = returnNode.getLineNumber();
                    final long retToken = returnNode.getToken();
                    // Expression is evaluated for side effects.
                    newStatements.add(new ExpressionStatement(retLineNumber, retToken, returnNode.getFinish(), expr));
                    newStatements.add(createJumpToInlinedFinally(fn, inlinedFinallies, ensureUniqueNamesIn(finallyBlock)));
                    return new BlockStatement(retLineNumber, new Block(retToken, finallyBlock.getFinish(), newStatements));
                } else if (expr == null || expr instanceof PrimitiveLiteralNode<?> || (expr instanceof IdentNode && RETURN.symbolName().equals(((IdentNode)expr).getName()))) {
                    // Nonterminal finally; no return expression, or returns a primitive literal, or returns :return.
                    // Just move the return expression into the finally block.
                    return createJumpToInlinedFinally(fn, inlinedFinallies, prependFinally(finallyBlock, returnNode));
                } else {
                    // We need to evaluate the result of the return in case it is complex while still in the try block,
                    // store it in :return, and return it afterwards.
                    final List<Statement> newStatements = new ArrayList<>();
                    final int retLineNumber = returnNode.getLineNumber();
                    final long retToken = returnNode.getToken();
                    final int retFinish = returnNode.getFinish();
                    final Expression resultNode = new IdentNode(expr.getToken(), expr.getFinish(), RETURN.symbolName());
                    // ":return = <expr>;"
                    newStatements.add(new ExpressionStatement(retLineNumber, retToken, retFinish, new BinaryNode(Token.recast(returnNode.getToken(), TokenType.ASSIGN), resultNode, expr)));
                    // inline finally and end it with "return :return;"
                    newStatements.add(createJumpToInlinedFinally(fn, inlinedFinallies, prependFinally(finallyBlock, returnNode.setExpression(resultNode))));
                    return new BlockStatement(retLineNumber, new Block(retToken, retFinish, newStatements));
                }
            }
        });
        addStatement(inlinedFinallies.isEmpty() ? newTryNode : newTryNode.setInlinedFinallies(lc, inlinedFinallies));
        // TODO: if finallyStatement is terminal, we could just have sites of inlined finallies jump here.
        addStatement(new BlockStatement(finallyBlock));

        return newTryNode;
    }

    private static JumpToInlinedFinally createJumpToInlinedFinally(final FunctionNode fn, final List<Block> inlinedFinallies, final Block finallyBlock) {
        final String labelName = fn.uniqueName(":finally");
        final long token = finallyBlock.getToken();
        final int finish = finallyBlock.getFinish();
        inlinedFinallies.add(new Block(token, finish, new LabelNode(finallyBlock.getFirstStatementLineNumber(),
                token, finish, labelName, finallyBlock)));
        return new JumpToInlinedFinally(labelName);
    }

    private static Block prependFinally(final Block finallyBlock, final Statement statement) {
        final Block inlinedFinally = ensureUniqueNamesIn(finallyBlock);
        if (isTerminalFinally(finallyBlock)) {
            return inlinedFinally;
        }
        final List<Statement> stmts = inlinedFinally.getStatements();
        final List<Statement> newStmts = new ArrayList<>(stmts.size() + 1);
        newStmts.addAll(stmts);
        newStmts.add(statement);
        return new Block(inlinedFinally.getToken(), statement.getFinish(), newStmts);
    }

    @Override
    public Node leaveTryNode(final TryNode tryNode) {
        final Block finallyBody = tryNode.getFinallyBody();
        TryNode newTryNode = tryNode.setFinallyBody(lc, null);

        // No finally or empty finally
        if (finallyBody == null || finallyBody.getStatementCount() == 0) {
            final List<CatchNode> catches = newTryNode.getCatches();
            if (catches == null || catches.isEmpty()) {
                // A completely degenerate try block: empty finally, no catches. Replace it with try body.
                return addStatement(new BlockStatement(tryNode.getBody()));
            }
            return addStatement(ensureUnconditionalCatch(newTryNode));
        }

        /*
         * create a new try node
         *    if we have catches:
         *
         *    try            try
         *       x              try
         *    catch               x
         *       y              catch
         *    finally z           y
         *                   catchall
         *                        rethrow
         *
         *   otherwise
         *
         *   try              try
         *      x               x
         *   finally          catchall
         *      y               rethrow
         *
         *
         *   now splice in finally code wherever needed
         *
         */
        final Block catchAll = catchAllBlock(tryNode);

        final List<ThrowNode> rethrows = new ArrayList<>(1);
        catchAll.accept(new SimpleNodeVisitor() {
            @Override
            public boolean enterThrowNode(final ThrowNode throwNode) {
                rethrows.add(throwNode);
                return true;
            }
        });
        assert rethrows.size() == 1;

        if (!tryNode.getCatchBlocks().isEmpty()) {
            final Block outerBody = new Block(newTryNode.getToken(), newTryNode.getFinish(), ensureUnconditionalCatch(newTryNode));
            newTryNode = newTryNode.setBody(lc, outerBody).setCatchBlocks(lc, null);
        }

        newTryNode = newTryNode.setCatchBlocks(lc, Arrays.asList(catchAll));

        /*
         * Now that the transform is done, we have to go into the try and splice
         * the finally block in front of any statement that is outside the try
         */
        return (TryNode)lc.replace(tryNode, spliceFinally(newTryNode, rethrows.get(0), finallyBody));
    }

    private TryNode ensureUnconditionalCatch(final TryNode tryNode) {
        final List<CatchNode> catches = tryNode.getCatches();
        if(catches == null || catches.isEmpty() || catches.get(catches.size() - 1).getExceptionCondition() == null) {
            return tryNode;
        }
        // If the last catch block is conditional, add an unconditional rethrow block
        final List<Block> newCatchBlocks = new ArrayList<>(tryNode.getCatchBlocks());

        newCatchBlocks.add(catchAllBlock(tryNode));
        return tryNode.setCatchBlocks(lc, newCatchBlocks);
    }

    @Override
    public boolean enterUnaryNode(final UnaryNode unaryNode) {
        if (es6) {
            if (unaryNode.isTokenType(TokenType.YIELD) ||
                unaryNode.isTokenType(TokenType.YIELD_STAR)) {
                throwNotImplementedYet("es6.yield", unaryNode);
            } else if (unaryNode.isTokenType(TokenType.SPREAD_ARGUMENT) ||
                       unaryNode.isTokenType(TokenType.SPREAD_ARRAY)) {
                throwNotImplementedYet("es6.spread", unaryNode);
            }
        }

        return super.enterUnaryNode(unaryNode);
    }

    @Override
    public boolean enterASSIGN(BinaryNode binaryNode) {
        if (es6 && (binaryNode.lhs() instanceof ObjectNode || binaryNode.lhs() instanceof ArrayLiteralNode)) {
            throwNotImplementedYet("es6.destructuring", binaryNode);
        }
        return super.enterASSIGN(binaryNode);
    }

    @Override
    public Node leaveVarNode(final VarNode varNode) {
        addStatement(varNode);
        if (varNode.getFlag(VarNode.IS_LAST_FUNCTION_DECLARATION)
                && lc.getCurrentFunction().isProgram()
                && ((FunctionNode) varNode.getInit()).isAnonymous()) {
            new ExpressionStatement(varNode.getLineNumber(), varNode.getToken(), varNode.getFinish(), new IdentNode(varNode.getName())).accept(this);
        }
        return varNode;
    }

    @Override
    public Node leaveWhileNode(final WhileNode whileNode) {
        final Expression test = whileNode.getTest();
        final Block body = whileNode.getBody();

        if (isAlwaysTrue(test)) {
            //turn it into a for node without a test.
            final ForNode forNode = (ForNode)new ForNode(whileNode.getLineNumber(), whileNode.getToken(), whileNode.getFinish(), body, 0).accept(this);
            lc.replace(whileNode, forNode);
            return forNode;
        }

         return addStatement(checkEscape(whileNode));
    }

    @Override
    public Node leaveWithNode(final WithNode withNode) {
        return addStatement(withNode);
    }

    @Override
    public boolean enterClassNode(final ClassNode classNode) {
        throwNotImplementedYet("es6.class", classNode);
        return super.enterClassNode(classNode);
    }

    
Given a function node that is a callee in a CallNode, replace it with the appropriate marker function. This is used by CodeGenerator for fast scope calls 
Params:
function – function called by a CallNode
Returns:
transformed node to marker function or identity if not ident/access/indexnode/**
     * Given a function node that is a callee in a CallNode, replace it with
     * the appropriate marker function. This is used by {@link CodeGenerator}
     * for fast scope calls
     *
     * @param function function called by a CallNode
     * @return transformed node to marker function or identity if not ident/access/indexnode
     */
    private static Expression markerFunction(final Expression function) {
        if (function instanceof IdentNode) {
            return ((IdentNode)function).setIsFunction();
        } else if (function instanceof BaseNode) {
            return ((BaseNode)function).setIsFunction();
        }
        return function;
    }

    
Calculate a synthetic eval location for a node for the stacktrace, for example src#17
Params:
node – a node
Returns:
eval location/**
     * Calculate a synthetic eval location for a node for the stacktrace, for example src#17<eval>
     * @param node a node
     * @return eval location
     */
    private String evalLocation(final IdentNode node) {
        final Source source = lc.getCurrentFunction().getSource();
        final int pos = node.position();
        return new StringBuilder().
            append(source.getName()).
            append('#').
            append(source.getLine(pos)).
            append(':').
            append(source.getColumn(pos)).
            append("<eval>").
            toString();
    }

    
Check whether a call node may be a call to eval. In that case we clone the args in order to create the following construct in CodeGenerator 
if (calledFuntion == buildInEval) {
   eval(cloned arg);
} else {
   cloned arg;
}

Params:
callNode – call node to check if it's an eval/**
     * Check whether a call node may be a call to eval. In that case we
     * clone the args in order to create the following construct in
     * {@link CodeGenerator}
     *
     * <pre>
     * if (calledFuntion == buildInEval) {
     *    eval(cloned arg);
     * } else {
     *    cloned arg;
     * }
     * </pre>
     *
     * @param callNode call node to check if it's an eval
     */
    private CallNode checkEval(final CallNode callNode) {
        if (callNode.getFunction() instanceof IdentNode) {

            final List<Expression> args = callNode.getArgs();
            final IdentNode callee = (IdentNode)callNode.getFunction();

            // 'eval' call with at least one argument
            if (args.size() >= 1 && EVAL.symbolName().equals(callee.getName())) {
                final List<Expression> evalArgs = new ArrayList<>(args.size());
                for(final Expression arg: args) {
                    evalArgs.add((Expression)ensureUniqueNamesIn(arg).accept(this));
                }
                return callNode.setEvalArgs(new CallNode.EvalArgs(evalArgs, evalLocation(callee)));
            }
        }

        return callNode;
    }

    
Helper that given a loop body makes sure that it is not terminal if it
has a continue that leads to the loop header or to outer loops' loop
headers. This means that, even if the body ends with a terminal
statement, we cannot tag it as terminal
Params:
loopBody – the loop body to check
Returns:
true if control flow may escape the loop/**
     * Helper that given a loop body makes sure that it is not terminal if it
     * has a continue that leads to the loop header or to outer loops' loop
     * headers. This means that, even if the body ends with a terminal
     * statement, we cannot tag it as terminal
     *
     * @param loopBody the loop body to check
     * @return true if control flow may escape the loop
     */
    private static boolean controlFlowEscapes(final LexicalContext lex, final Block loopBody) {
        final List<Node> escapes = new ArrayList<>();

        loopBody.accept(new SimpleNodeVisitor() {
            @Override
            public Node leaveBreakNode(final BreakNode node) {
                escapes.add(node);
                return node;
            }

            @Override
            public Node leaveContinueNode(final ContinueNode node) {
                // all inner loops have been popped.
                if (lex.contains(node.getTarget(lex))) {
                    escapes.add(node);
                }
                return node;
            }
        });

        return !escapes.isEmpty();
    }

    @SuppressWarnings("unchecked")
    private <T extends LoopNode> T checkEscape(final T loopNode) {
        final boolean escapes = controlFlowEscapes(lc, loopNode.getBody());
        if (escapes) {
            return (T)loopNode.
                setBody(lc, loopNode.getBody().setIsTerminal(lc, false)).
                setControlFlowEscapes(lc, escapes);
        }
        return loopNode;
    }


    private Node addStatement(final Statement statement) {
        lc.appendStatement(statement);
        return statement;
    }

    private void addStatementEnclosedInBlock(final Statement stmt) {
        BlockStatement b = BlockStatement.createReplacement(stmt, Collections.<Statement>singletonList(stmt));
        if(stmt.isTerminal()) {
            b = b.setBlock(b.getBlock().setIsTerminal(null, true));
        }
        addStatement(b);
    }

    
An internal expression has a symbol that is tagged internal. Check if
this is such a node
Params:
expression – expression to check for internal symbol
Returns:
true if internal, false otherwise/**
     * An internal expression has a symbol that is tagged internal. Check if
     * this is such a node
     *
     * @param expression expression to check for internal symbol
     * @return true if internal, false otherwise
     */
    private static boolean isInternalExpression(final Expression expression) {
        if (!(expression instanceof IdentNode)) {
            return false;
        }
        final Symbol symbol = ((IdentNode)expression).getSymbol();
        return symbol != null && symbol.isInternal();
    }

    
Is this an assignment to the special variable that hosts scripting eval
results, i.e. __return__?
Params:
expression – expression to check whether it is $evalresult = X
Returns:
true if an assignment to eval result, false otherwise/**
     * Is this an assignment to the special variable that hosts scripting eval
     * results, i.e. __return__?
     *
     * @param expression expression to check whether it is $evalresult = X
     * @return true if an assignment to eval result, false otherwise
     */
    private static boolean isEvalResultAssignment(final Node expression) {
        final Node e = expression;
        if (e instanceof BinaryNode) {
            final Node lhs = ((BinaryNode)e).lhs();
            if (lhs instanceof IdentNode) {
                return ((IdentNode)lhs).getName().equals(RETURN.symbolName());
            }
        }
        return false;
    }

    private void throwNotImplementedYet(final String msgId, final Node node) {
        final long token = node.getToken();
        final int line = source.getLine(node.getStart());
        final int column = source.getColumn(node.getStart());
        final String message = ECMAErrors.getMessage("unimplemented." + msgId);
        final String formatted = ErrorManager.format(message, source, line, column, token);
        throw new RuntimeException(formatted);
    }
}