var esprima = {};
 (function (exports) {
    'use strict';

    var Token,
        TokenName,
        FnExprTokens,
        Syntax,
        PlaceHolders,
        Messages,
        Regex,
        source,
        strict,
        index,
        lineNumber,
        lineStart,
        hasLineTerminator,
        lastIndex,
        lastLineNumber,
        lastLineStart,
        startIndex,
        startLineNumber,
        startLineStart,
        scanning,
        length,
        lookahead,
        state,
        extra,
        isBindingElement,
        isAssignmentTarget,
        firstCoverInitializedNameError;

    Token = {
        BooleanLiteral: 1,
        EOF: 2,
        Identifier: 3,
        Keyword: 4,
        NullLiteral: 5,
        NumericLiteral: 6,
        Punctuator: 7,
        StringLiteral: 8,
        RegularExpression: 9,
        Template: 10
    };

    TokenName = {};
    TokenName[Token.BooleanLiteral] = 'Boolean';
    TokenName[Token.EOF] = '<end>';
    TokenName[Token.Identifier] = 'Identifier';
    TokenName[Token.Keyword] = 'Keyword';
    TokenName[Token.NullLiteral] = 'Null';
    TokenName[Token.NumericLiteral] = 'Numeric';
    TokenName[Token.Punctuator] = 'Punctuator';
    TokenName[Token.StringLiteral] = 'String';
    TokenName[Token.RegularExpression] = 'RegularExpression';
    TokenName[Token.Template] = 'Template';

    FnExprTokens = ['(', '{', '[', 'in', 'typeof', 'instanceof', 'new',
        'return', 'case', 'delete', 'throw', 'void',
        '=', '+=', '-=', '*=', '/=', '%=', '<<=', '>>=', '>>>=',
        '&=', '|=', '^=', ',',
        '+', '-', '*', '/', '%', '++', '--', '<<', '>>', '>>>', '&',
        '|', '^', '!', '~', '&&', '||', '?', ':', '===', '==', '>=',
        '<=', '<', '>', '!=', '!=='];

    Syntax = {
        AssignmentExpression: 'AssignmentExpression',
        AssignmentPattern: 'AssignmentPattern',
        ArrayExpression: 'ArrayExpression',
        ArrayPattern: 'ArrayPattern',
        ArrowFunctionExpression: 'ArrowFunctionExpression',
        BlockStatement: 'BlockStatement',
        BinaryExpression: 'BinaryExpression',
        BreakStatement: 'BreakStatement',
        CallExpression: 'CallExpression',
        CatchClause: 'CatchClause',
        ClassBody: 'ClassBody',
        ClassDeclaration: 'ClassDeclaration',
        ClassExpression: 'ClassExpression',
        ConditionalExpression: 'ConditionalExpression',
        ContinueStatement: 'ContinueStatement',
        DoWhileStatement: 'DoWhileStatement',
        DebuggerStatement: 'DebuggerStatement',
        EmptyStatement: 'EmptyStatement',
        ExportAllDeclaration: 'ExportAllDeclaration',
        ExportDefaultDeclaration: 'ExportDefaultDeclaration',
        ExportNamedDeclaration: 'ExportNamedDeclaration',
        ExportSpecifier: 'ExportSpecifier',
        ExpressionStatement: 'ExpressionStatement',
        ForStatement: 'ForStatement',
        ForOfStatement: 'ForOfStatement',
        ForInStatement: 'ForInStatement',
        FunctionDeclaration: 'FunctionDeclaration',
        FunctionExpression: 'FunctionExpression',
        Identifier: 'Identifier',
        IfStatement: 'IfStatement',
        ImportDeclaration: 'ImportDeclaration',
        ImportDefaultSpecifier: 'ImportDefaultSpecifier',
        ImportNamespaceSpecifier: 'ImportNamespaceSpecifier',
        ImportSpecifier: 'ImportSpecifier',
        Literal: 'Literal',
        LabeledStatement: 'LabeledStatement',
        LogicalExpression: 'LogicalExpression',
        MemberExpression: 'MemberExpression',
        MetaProperty: 'MetaProperty',
        MethodDefinition: 'MethodDefinition',
        NewExpression: 'NewExpression',
        ObjectExpression: 'ObjectExpression',
        ObjectPattern: 'ObjectPattern',
        Program: 'Program',
        Property: 'Property',
        RestElement: 'RestElement',
        ReturnStatement: 'ReturnStatement',
        SequenceExpression: 'SequenceExpression',
        SpreadElement: 'SpreadElement',
        Super: 'Super',
        SwitchCase: 'SwitchCase',
        SwitchStatement: 'SwitchStatement',
        TaggedTemplateExpression: 'TaggedTemplateExpression',
        TemplateElement: 'TemplateElement',
        TemplateLiteral: 'TemplateLiteral',
        ThisExpression: 'ThisExpression',
        ThrowStatement: 'ThrowStatement',
        TryStatement: 'TryStatement',
        UnaryExpression: 'UnaryExpression',
        UpdateExpression: 'UpdateExpression',
        VariableDeclaration: 'VariableDeclaration',
        VariableDeclarator: 'VariableDeclarator',
        WhileStatement: 'WhileStatement',
        WithStatement: 'WithStatement',
        YieldExpression: 'YieldExpression'
    };

    PlaceHolders = {
        ArrowParameterPlaceHolder: 'ArrowParameterPlaceHolder'
    };

    Messages = {
        UnexpectedToken: 'Unexpected token %0',
        UnexpectedNumber: 'Unexpected number',
        UnexpectedString: 'Unexpected string',
        UnexpectedIdentifier: 'Unexpected identifier',
        UnexpectedReserved: 'Unexpected reserved word',
        UnexpectedTemplate: 'Unexpected quasi %0',
        UnexpectedEOS: 'Unexpected end of input',
        NewlineAfterThrow: 'Illegal newline after throw',
        InvalidRegExp: 'Invalid regular expression',
        UnterminatedRegExp: 'Invalid regular expression: missing /',
        InvalidLHSInAssignment: 'Invalid left-hand side in assignment',
        InvalidLHSInForIn: 'Invalid left-hand side in for-in',
        InvalidLHSInForLoop: 'Invalid left-hand side in for-loop',
        MultipleDefaultsInSwitch: 'More than one default clause in switch statement',
        NoCatchOrFinally: 'Missing catch or finally after try',
        UnknownLabel: 'Undefined label \'%0\'',
        Redeclaration: '%0 \'%1\' has already been declared',
        IllegalContinue: 'Illegal continue statement',
        IllegalBreak: 'Illegal break statement',
        IllegalReturn: 'Illegal return statement',
        StrictModeWith: 'Strict mode code may not include a with statement',
        StrictCatchVariable: 'Catch variable may not be eval or arguments in strict mode',
        StrictVarName: 'Variable name may not be eval or arguments in strict mode',
        StrictParamName: 'Parameter name eval or arguments is not allowed in strict mode',
        StrictParamDupe: 'Strict mode function may not have duplicate parameter names',
        StrictFunctionName: 'Function name may not be eval or arguments in strict mode',
        StrictOctalLiteral: 'Octal literals are not allowed in strict mode.',
        StrictDelete: 'Delete of an unqualified identifier in strict mode.',
        StrictLHSAssignment: 'Assignment to eval or arguments is not allowed in strict mode',
        StrictLHSPostfix: 'Postfix increment/decrement may not have eval or arguments operand in strict mode',
        StrictLHSPrefix: 'Prefix increment/decrement may not have eval or arguments operand in strict mode',
        StrictReservedWord: 'Use of future reserved word in strict mode',
        TemplateOctalLiteral: 'Octal literals are not allowed in template strings.',
        ParameterAfterRestParameter: 'Rest parameter must be last formal parameter',
        DefaultRestParameter: 'Unexpected token =',
        ObjectPatternAsRestParameter: 'Unexpected token {',
        DuplicateProtoProperty: 'Duplicate __proto__ fields are not allowed in object literals',
        ConstructorSpecialMethod: 'Class constructor may not be an accessor',
        DuplicateConstructor: 'A class may only have one constructor',
        StaticPrototype: 'Classes may not have static property named prototype',
        MissingFromClause: 'Unexpected token',
        NoAsAfterImportNamespace: 'Unexpected token',
        InvalidModuleSpecifier: 'Unexpected token',
        IllegalImportDeclaration: 'Unexpected token',
        IllegalExportDeclaration: 'Unexpected token',
        DuplicateBinding: 'Duplicate binding %0'
    };

    Regex = {
        NonAsciiIdentifierStart: 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E2B\uDEB0-\uDEDE\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3D\uDF5D-\uDF61]|\uD805[\uDC80-\uDCAF\uDCC4\uDCC5\uDCC7\uDD80-\uDDAE\uDE00-\uDE2F\uDE44\uDE80-\uDEAA]|\uD806[\uDCA0-\uDCDF\uDCFF\uDEC0-\uDEF8]|\uD808[\uDC00-\uDF98]|\uD809[\uDC00-\uDC6E]|[\uD80C\uD840-\uD868\uD86A-\uD86C][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDED0-\uDEED\uDF00-\uDF2F\uDF40-\uDF43\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDF00-\uDF44\uDF50\uDF93-\uDF9F]|\uD82C[\uDC00\uDC01]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99]|\uD835[\uDC00-\uDC54\uDC56-\uDC9C\uDC9E\uDC9F\uDCA2\uDCA5\uDCA6\uDCA9-\uDCAC\uDCAE-\uDCB9\uDCBB\uDCBD-\uDCC3\uDCC5-\uDD05\uDD07-\uDD0A\uDD0D-\uDD14\uDD16-\uDD1C\uDD1E-\uDD39\uDD3B-\uDD3E\uDD40-\uDD44\uDD46\uDD4A-\uDD50\uDD52-\uDEA5\uDEA8-\uDEC0\uDEC2-\uDEDA\uDEDC-\uDEFA\uDEFC-\uDF14\uDF16-\uDF34\uDF36-\uDF4E\uDF50-\uDF6E\uDF70-\uDF88\uDF8A-\uDFA8\uDFAA-\uDFC2\uDFC4-\uDFCB]|\uD83A[\uDC00-\uDCC4]|\uD83B[\uDE00-\uDE03\uDE05-\uDE1F\uDE21\uDE22\uDE24\uDE27\uDE29-\uDE32\uDE34-\uDE37\uDE39\uDE3B\uDE42\uDE47\uDE49\uDE4B\uDE4D-\uDE4F\uDE51\uDE52\uDE54\uDE57\uDE59\uDE5B\uDE5D\uDE5F\uDE61\uDE62\uDE64\uDE67-\uDE6A\uDE6C-\uDE72\uDE74-\uDE77\uDE79-\uDE7C\uDE7E\uDE80-\uDE89\uDE8B-\uDE9B\uDEA1-\uDEA3\uDEA5-\uDEA9\uDEAB-\uDEBB]|\uD869[\uDC00-\uDED6\uDF00-\uDFFF]|\uD86D[\uDC00-\uDF34\uDF40-\uDFFF]|\uD86E[\uDC00-\uDC1D]|\uD87E[\uDC00-\uDE1D]/,

        NonAsciiIdentifierPart: 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    };

    function assert(condition, message) {
        if (!condition) {
            throw new Error('ASSERT: ' + message);
        }
    }

    function isDecimalDigit(ch) {
        return (ch >= 0x30 && ch <= 0x39);
    }

    function isHexDigit(ch) {
        return '0123456789abcdefABCDEF'.indexOf(ch) >= 0;
    }

    function isOctalDigit(ch) {
        return '01234567'.indexOf(ch) >= 0;
    }

    function octalToDecimal(ch) {
        var octal = (ch !== '0'), code = '01234567'.indexOf(ch);

        if (index < length && isOctalDigit(source[index])) {
            octal = true;
            code = code * 8 + '01234567'.indexOf(source[index++]);

            if ('0123'.indexOf(ch) >= 0 &&
                index < length &&
                isOctalDigit(source[index])) {
                code = code * 8 + '01234567'.indexOf(source[index++]);
            }
        }

        return {
            code: code,
            octal: octal
        };
    }

    function isWhiteSpace(ch) {
        return (ch === 0x20) || (ch === 0x09) || (ch === 0x0B) || (ch === 0x0C) || (ch === 0xA0) ||
            (ch >= 0x1680 && [0x1680, 0x180E, 0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008, 0x2009, 0x200A, 0x202F, 0x205F, 0x3000, 0xFEFF].indexOf(ch) >= 0);
    }


    function isLineTerminator(ch) {
        return (ch === 0x0A) || (ch === 0x0D) || (ch === 0x2028) || (ch === 0x2029);
    }


    function fromCodePoint(cp) {
        return (cp < 0x10000) ? String.fromCharCode(cp) :
        String.fromCharCode(0xD800 + ((cp - 0x10000) >> 10)) +
        String.fromCharCode(0xDC00 + ((cp - 0x10000) & 1023));
    }

    function isIdentifierStart(ch) {
        return (ch === 0x24) || (ch === 0x5F) ||
            (ch >= 0x41 && ch <= 0x5A) ||
            (ch >= 0x61 && ch <= 0x7A) ||
            (ch === 0x5C) ||
            ((ch >= 0x80) && Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch)));
    }

    function isIdentifierPart(ch) {
        return (ch === 0x24) || (ch === 0x5F) ||
            (ch >= 0x41 && ch <= 0x5A) ||
            (ch >= 0x61 && ch <= 0x7A) ||
            (ch >= 0x30 && ch <= 0x39) ||
            (ch === 0x5C) ||
            ((ch >= 0x80) && Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch)));
    }


    function isFutureReservedWord(id) {
        switch (id) {
            case 'enum':
            case 'export':
            case 'import':
            case 'super':
                return true;
            default:
                return false;
        }
    }

    function isStrictModeReservedWord(id) {
        switch (id) {
            case 'implements':
            case 'interface':
            case 'package':
            case 'private':
            case 'protected':
            case 'public':
            case 'static':
            case 'yield':
            case 'let':
                return true;
            default:
                return false;
        }
    }

    function isRestrictedWord(id) {
        return id === 'eval' || id === 'arguments';
    }


    function isKeyword(id) {
        switch (id.length) {
            case 2:
                return (id === 'if') || (id === 'in') || (id === 'do');
            case 3:
                return (id === 'var') || (id === 'for') || (id === 'new') ||
                    (id === 'try') || (id === 'let');
            case 4:
                return (id === 'this') || (id === 'else') || (id === 'case') ||
                    (id === 'void') || (id === 'with') || (id === 'enum');
            case 5:
                return (id === 'while') || (id === 'break') || (id === 'catch') ||
                    (id === 'throw') || (id === 'const') || (id === 'yield') ||
                    (id === 'class') || (id === 'super');
            case 6:
                return (id === 'return') || (id === 'typeof') || (id === 'delete') ||
                    (id === 'switch') || (id === 'export') || (id === 'import');
            case 7:
                return (id === 'default') || (id === 'finally') || (id === 'extends');
            case 8:
                return (id === 'function') || (id === 'continue') || (id === 'debugger');
            case 10:
                return (id === 'instanceof');
            default:
                return false;
        }
    }


    function addComment(type, value, start, end, loc) {
        var comment;

        assert(typeof start === 'number', 'Comment must have valid position');

        state.lastCommentStart = start;

        comment = {
            type: type,
            value: value
        };
        if (extra.range) {
            comment.range = [start, end];
        }
        if (extra.loc) {
            comment.loc = loc;
        }
        extra.comments.push(comment);
        if (extra.attachComment) {
            extra.leadingComments.push(comment);
            extra.trailingComments.push(comment);
        }
    }

    function skipSingleLineComment(offset) {
        var start, loc, ch, comment;

        start = index - offset;
        loc = {
            start: {
                line: lineNumber,
                column: index - lineStart - offset
            }
        };

        while (index < length) {
            ch = source.charCodeAt(index);
            ++index;
            if (isLineTerminator(ch)) {
                hasLineTerminator = true;
                if (extra.comments) {
                    comment = source.slice(start + offset, index - 1);
                    loc.end = {
                        line: lineNumber,
                        column: index - lineStart - 1
                    };
                    addComment('Line', comment, start, index - 1, loc);
                }
                if (ch === 13 && source.charCodeAt(index) === 10) {
                    ++index;
                }
                ++lineNumber;
                lineStart = index;
                return;
            }
        }

        if (extra.comments) {
            comment = source.slice(start + offset, index);
            loc.end = {
                line: lineNumber,
                column: index - lineStart
            };
            addComment('Line', comment, start, index, loc);
        }
    }

    function skipMultiLineComment() {
        var start, loc, ch, comment;

        if (extra.comments) {
            start = index - 2;
            loc = {
                start: {
                    line: lineNumber,
                    column: index - lineStart - 2
                }
            };
        }

        while (index < length) {
            ch = source.charCodeAt(index);
            if (isLineTerminator(ch)) {
                if (ch === 0x0D && source.charCodeAt(index + 1) === 0x0A) {
                    ++index;
                }
                hasLineTerminator = true;
                ++lineNumber;
                ++index;
                lineStart = index;
            } else if (ch === 0x2A) {
                if (source.charCodeAt(index + 1) === 0x2F) {
                    ++index;
                    ++index;
                    if (extra.comments) {
                        comment = source.slice(start + 2, index - 2);
                        loc.end = {
                            line: lineNumber,
                            column: index - lineStart
                        };
                        addComment('Block', comment, start, index, loc);
                    }
                    return;
                }
                ++index;
            } else {
                ++index;
            }
        }

        if (extra.comments) {
            loc.end = {
                line: lineNumber,
                column: index - lineStart
            };
            comment = source.slice(start + 2, index);
            addComment('Block', comment, start, index, loc);
        }
        tolerateUnexpectedToken();
    }

    function skipComment() {
        var ch, start;
        hasLineTerminator = false;

        start = (index === 0);
        while (index < length) {
            ch = source.charCodeAt(index);

            if (isWhiteSpace(ch)) {
                ++index;
            } else if (isLineTerminator(ch)) {
                hasLineTerminator = true;
                ++index;
                if (ch === 0x0D && source.charCodeAt(index) === 0x0A) {
                    ++index;
                }
                ++lineNumber;
                lineStart = index;
                start = true;
            } else if (ch === 0x2F) {
                ch = source.charCodeAt(index + 1);
                if (ch === 0x2F) {
                    ++index;
                    ++index;
                    skipSingleLineComment(2);
                    start = true;
                } else if (ch === 0x2A) {
                    ++index;
                    ++index;
                    skipMultiLineComment();
                } else {
                    break;
                }
            } else if (start && ch === 0x2D) {
                if ((source.charCodeAt(index + 1) === 0x2D) && (source.charCodeAt(index + 2) === 0x3E)) {
                    index += 3;
                    skipSingleLineComment(3);
                } else {
                    break;
                }
            } else if (ch === 0x3C) {
                if (source.slice(index + 1, index + 4) === '!--') {
                    ++index;
                    ++index;
                    ++index;
                    ++index;
                    skipSingleLineComment(4);
                } else {
                    break;
                }
            } else {
                break;
            }
        }
    }

    function scanHexEscape(prefix) {
        var i, len, ch, code = 0;

        len = (prefix === 'u') ? 4 : 2;
        for (i = 0; i < len; ++i) {
            if (index < length && isHexDigit(source[index])) {
                ch = source[index++];
                code = code * 16 + '0123456789abcdef'.indexOf(ch.toLowerCase());
            } else {
                return '';
            }
        }
        return String.fromCharCode(code);
    }

    function scanUnicodeCodePointEscape() {
        var ch, code;

        ch = source[index];
        code = 0;

        if (ch === '}') {
            throwUnexpectedToken();
        }

        while (index < length) {
            ch = source[index++];
            if (!isHexDigit(ch)) {
                break;
            }
            code = code * 16 + '0123456789abcdef'.indexOf(ch.toLowerCase());
        }

        if (code > 0x10FFFF || ch !== '}') {
            throwUnexpectedToken();
        }

        return fromCodePoint(code);
    }

    function codePointAt(i) {
        var cp, first, second;

        cp = source.charCodeAt(i);
        if (cp >= 0xD800 && cp <= 0xDBFF) {
            second = source.charCodeAt(i + 1);
            if (second >= 0xDC00 && second <= 0xDFFF) {
                first = cp;
                cp = (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000;
            }
        }

        return cp;
    }

    function getComplexIdentifier() {
        var cp, ch, id;

        cp = codePointAt(index);
        id = fromCodePoint(cp);
        index += id.length;

        if (cp === 0x5C) {
            if (source.charCodeAt(index) !== 0x75) {
                throwUnexpectedToken();
            }
            ++index;
            if (source[index] === '{') {
                ++index;
                ch = scanUnicodeCodePointEscape();
            } else {
                ch = scanHexEscape('u');
                cp = ch.charCodeAt(0);
                if (!ch || ch === '\\' || !isIdentifierStart(cp)) {
                    throwUnexpectedToken();
                }
            }
            id = ch;
        }

        while (index < length) {
            cp = codePointAt(index);
            if (!isIdentifierPart(cp)) {
                break;
            }
            ch = fromCodePoint(cp);
            id += ch;
            index += ch.length;

            if (cp === 0x5C) {
                id = id.substr(0, id.length - 1);
                if (source.charCodeAt(index) !== 0x75) {
                    throwUnexpectedToken();
                }
                ++index;
                if (source[index] === '{') {
                    ++index;
                    ch = scanUnicodeCodePointEscape();
                } else {
                    ch = scanHexEscape('u');
                    cp = ch.charCodeAt(0);
                    if (!ch || ch === '\\' || !isIdentifierPart(cp)) {
                        throwUnexpectedToken();
                    }
                }
                id += ch;
            }
        }

        return id;
    }

    function getIdentifier() {
        var start, ch;

        start = index++;
        while (index < length) {
            ch = source.charCodeAt(index);
            if (ch === 0x5C) {
                index = start;
                return getComplexIdentifier();
            } else if (ch >= 0xD800 && ch < 0xDFFF) {
                index = start;
                return getComplexIdentifier();
            }
            if (isIdentifierPart(ch)) {
                ++index;
            } else {
                break;
            }
        }

        return source.slice(start, index);
    }

    function scanIdentifier() {
        var start, id, type;

        start = index;

        id = (source.charCodeAt(index) === 0x5C) ? getComplexIdentifier() : getIdentifier();

        if (id.length === 1) {
            type = Token.Identifier;
        } else if (isKeyword(id)) {
            type = Token.Keyword;
        } else if (id === 'null') {
            type = Token.NullLiteral;
        } else if (id === 'true' || id === 'false') {
            type = Token.BooleanLiteral;
        } else {
            type = Token.Identifier;
        }

        return {
            type: type,
            value: id,
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }


    function scanPunctuator() {
        var token, str;

        token = {
            type: Token.Punctuator,
            value: '',
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: index,
            end: index
        };

        str = source[index];
        switch (str) {

            case '(':
                if (extra.tokenize) {
                    extra.openParenToken = extra.tokens.length;
                }
                ++index;
                break;

            case '{':
                if (extra.tokenize) {
                    extra.openCurlyToken = extra.tokens.length;
                }
                state.curlyStack.push('{');
                ++index;
                break;

            case '.':
                ++index;
                if (source[index] === '.' && source[index + 1] === '.') {
                    index += 2;
                    str = '...';
                }
                break;

            case '}':
                ++index;
                state.curlyStack.pop();
                break;
            case ')':
            case ';':
            case ',':
            case '[':
            case ']':
            case ':':
            case '?':
            case '~':
                ++index;
                break;

            default:
                str = source.substr(index, 4);
                if (str === '>>>=') {
                    index += 4;
                } else {

                    str = str.substr(0, 3);
                    if (str === '===' || str === '!==' || str === '>>>' ||
                        str === '<<=' || str === '>>=') {
                        index += 3;
                    } else {

                        str = str.substr(0, 2);
                        if (str === '&&' || str === '||' || str === '==' || str === '!=' ||
                            str === '+=' || str === '-=' || str === '*=' || str === '/=' ||
                            str === '++' || str === '--' || str === '<<' || str === '>>' ||
                            str === '&=' || str === '|=' || str === '^=' || str === '%=' ||
                            str === '<=' || str === '>=' || str === '=>') {
                            index += 2;
                        } else {

                            str = source[index];
                            if ('<>=!+-*%&|^/'.indexOf(str) >= 0) {
                                ++index;
                            }
                        }
                    }
                }
        }

        if (index === token.start) {
            throwUnexpectedToken();
        }

        token.end = index;
        token.value = str;
        return token;
    }


    function scanHexLiteral(start) {
        var number = '';

        while (index < length) {
            if (!isHexDigit(source[index])) {
                break;
            }
            number += source[index++];
        }

        if (number.length === 0) {
            throwUnexpectedToken();
        }

        if (isIdentifierStart(source.charCodeAt(index))) {
            throwUnexpectedToken();
        }

        return {
            type: Token.NumericLiteral,
            value: parseInt('0x' + number, 16),
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }

    function scanBinaryLiteral(start) {
        var ch, number;

        number = '';

        while (index < length) {
            ch = source[index];
            if (ch !== '0' && ch !== '1') {
                break;
            }
            number += source[index++];
        }

        if (number.length === 0) {
            throwUnexpectedToken();
        }

        if (index < length) {
            ch = source.charCodeAt(index);
            if (isIdentifierStart(ch) || isDecimalDigit(ch)) {
                throwUnexpectedToken();
            }
        }

        return {
            type: Token.NumericLiteral,
            value: parseInt(number, 2),
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }

    function scanOctalLiteral(prefix, start) {
        var number, octal;

        if (isOctalDigit(prefix)) {
            octal = true;
            number = '0' + source[index++];
        } else {
            octal = false;
            ++index;
            number = '';
        }

        while (index < length) {
            if (!isOctalDigit(source[index])) {
                break;
            }
            number += source[index++];
        }

        if (!octal && number.length === 0) {
            throwUnexpectedToken();
        }

        if (isIdentifierStart(source.charCodeAt(index)) || isDecimalDigit(source.charCodeAt(index))) {
            throwUnexpectedToken();
        }

        return {
            type: Token.NumericLiteral,
            value: parseInt(number, 8),
            octal: octal,
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }

    function isImplicitOctalLiteral() {
        var i, ch;

        for (i = index + 1; i < length; ++i) {
            ch = source[i];
            if (ch === '8' || ch === '9') {
                return false;
            }
            if (!isOctalDigit(ch)) {
                return true;
            }
        }

        return true;
    }

    function scanNumericLiteral() {
        var number, start, ch;

        ch = source[index];
        assert(isDecimalDigit(ch.charCodeAt(0)) || (ch === '.'),
            'Numeric literal must start with a decimal digit or a decimal point');

        start = index;
        number = '';
        if (ch !== '.') {
            number = source[index++];
            ch = source[index];

            if (number === '0') {
                if (ch === 'x' || ch === 'X') {
                    ++index;
                    return scanHexLiteral(start);
                }
                if (ch === 'b' || ch === 'B') {
                    ++index;
                    return scanBinaryLiteral(start);
                }
                if (ch === 'o' || ch === 'O') {
                    return scanOctalLiteral(ch, start);
                }

                if (isOctalDigit(ch)) {
                    if (isImplicitOctalLiteral()) {
                        return scanOctalLiteral(ch, start);
                    }
                }
            }

            while (isDecimalDigit(source.charCodeAt(index))) {
                number += source[index++];
            }
            ch = source[index];
        }

        if (ch === '.') {
            number += source[index++];
            while (isDecimalDigit(source.charCodeAt(index))) {
                number += source[index++];
            }
            ch = source[index];
        }

        if (ch === 'e' || ch === 'E') {
            number += source[index++];

            ch = source[index];
            if (ch === '+' || ch === '-') {
                number += source[index++];
            }
            if (isDecimalDigit(source.charCodeAt(index))) {
                while (isDecimalDigit(source.charCodeAt(index))) {
                    number += source[index++];
                }
            } else {
                throwUnexpectedToken();
            }
        }

        if (isIdentifierStart(source.charCodeAt(index))) {
            throwUnexpectedToken();
        }

        return {
            type: Token.NumericLiteral,
            value: parseFloat(number),
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }


    function scanStringLiteral() {
        var str = '', quote, start, ch, unescaped, octToDec, octal = false;

        quote = source[index];
        assert((quote === '\'' || quote === '"'),
            'String literal must starts with a quote');

        start = index;
        ++index;

        while (index < length) {
            ch = source[index++];

            if (ch === quote) {
                quote = '';
                break;
            } else if (ch === '\\') {
                ch = source[index++];
                if (!ch || !isLineTerminator(ch.charCodeAt(0))) {
                    switch (ch) {
                        case 'u':
                        case 'x':
                            if (source[index] === '{') {
                                ++index;
                                str += scanUnicodeCodePointEscape();
                            } else {
                                unescaped = scanHexEscape(ch);
                                if (!unescaped) {
                                    throw throwUnexpectedToken();
                                }
                                str += unescaped;
                            }
                            break;
                        case 'n':
                            str += '\n';
                            break;
                        case 'r':
                            str += '\r';
                            break;
                        case 't':
                            str += '\t';
                            break;
                        case 'b':
                            str += '\b';
                            break;
                        case 'f':
                            str += '\f';
                            break;
                        case 'v':
                            str += '\x0B';
                            break;
                        case '8':
                        case '9':
                            str += ch;
                            tolerateUnexpectedToken();
                            break;

                        default:
                            if (isOctalDigit(ch)) {
                                octToDec = octalToDecimal(ch);

                                octal = octToDec.octal || octal;
                                str += String.fromCharCode(octToDec.code);
                            } else {
                                str += ch;
                            }
                            break;
                    }
                } else {
                    ++lineNumber;
                    if (ch === '\r' && source[index] === '\n') {
                        ++index;
                    }
                    lineStart = index;
                }
            } else if (isLineTerminator(ch.charCodeAt(0))) {
                break;
            } else {
                str += ch;
            }
        }

        if (quote !== '') {
            throwUnexpectedToken();
        }

        return {
            type: Token.StringLiteral,
            value: str,
            octal: octal,
            lineNumber: startLineNumber,
            lineStart: startLineStart,
            start: start,
            end: index
        };
    }


    function scanTemplate() {
        var cooked = '', ch, start, rawOffset, terminated, head, tail, restore, unescaped;

        terminated = false;
        tail = false;
        start = index;
        head = (source[index] === '`');
        rawOffset = 2;

        ++index;

        while (index < length) {
            ch = source[index++];
            if (ch === '`') {
                rawOffset = 1;
                tail = true;
                terminated = true;
                break;
            } else if (ch === '$') {
                if (source[index] === '{') {
                    state.curlyStack.push('${');
                    ++index;
                    terminated = true;
                    break;
                }
                cooked += ch;
            } else if (ch === '\\') {
                ch = source[index++];
                if (!isLineTerminator(ch.charCodeAt(0))) {
                    switch (ch) {
                        case 'n':
                            cooked += '\n';
                            break;
                        case 'r':
                            cooked += '\r';
                            break;
                        case 't':
                            cooked += '\t';
                            break;
                        case 'u':
                        case 'x':
                            if (source[index] === '{') {
                                ++index;
                                cooked += scanUnicodeCodePointEscape();
                            } else {
                                restore = index;
                                unescaped = scanHexEscape(ch);
                                if (unescaped) {
                                    cooked += unescaped;
                                } else {
                                    index = restore;
                                    cooked += ch;
                                }
                            }
                            break;
                        case 'b':
                            cooked += '\b';
                            break;
                        case 'f':
                            cooked += '\f';
                            break;
                        case 'v':
                            cooked += '\v';
                            break;

                        default:
                            if (ch === '0') {
                                if (isDecimalDigit(source.charCodeAt(index))) {
                                    throwError(Messages.TemplateOctalLiteral);
                                }
                                cooked += '\0';
                            } else if (isOctalDigit(ch)) {
                                throwError(Messages.TemplateOctalLiteral);
                            } else {
                                cooked += ch;
                            }
                            break;
                    }
                } else {
                    ++lineNumber;
                    if (ch === '\r' && source[index] === '\n') {
                        ++index;
                    }
                    lineStart = index;
                }
            } else if (isLineTerminator(ch.charCodeAt(0))) {
                ++lineNumber;
                if (ch === '\r' && source[index] === '\n') {
                    ++index;
                }
                lineStart = index;
                cooked += '\n';
            } else {
                cooked += ch;
            }
        }

        if (!terminated) {
            throwUnexpectedToken();
        }

        if (!head) {
            state.curlyStack.pop();
        }

        return {
            type: Token.Template,
            value: {
                cooked: cooked,
                raw: source.slice(start + 1, index - rawOffset)
            },
            head: head,
            tail: tail,
            lineNumber: lineNumber,
            lineStart: lineStart,
            start: start,
            end: index
        };
    }


    function testRegExp(pattern, flags) {
        var astralSubstitute = '\uFFFF',
            tmp = pattern;

        if (flags.indexOf('u') >= 0) {
            tmp = tmp
                .replace(/\\u\{([0-9a-fA-F]+)\}|\\u([a-fA-F0-9]{4})/g, function ($0, $1, $2) {
                    var codePoint = parseInt($1 || $2, 16);
                    if (codePoint > 0x10FFFF) {
                        throwUnexpectedToken(null, Messages.InvalidRegExp);
                    }
                    if (codePoint <= 0xFFFF) {
                        return String.fromCharCode(codePoint);
                    }
                    return astralSubstitute;
                })
                .replace(
                /[\uD800-\uDBFF][\uDC00-\uDFFF]/g,
                astralSubstitute
            );
        }

        try {
            RegExp(tmp);
        } catch (e) {
            throwUnexpectedToken(null, Messages.InvalidRegExp);
        }

        try {
            return new RegExp(pattern, flags);
        } catch (exception) {
            return null;
        }
    }

    function scanRegExpBody() {
        var ch, str, classMarker, terminated, body;

        ch = source[index];
        assert(ch === '/', 'Regular expression literal must start with a slash');
        str = source[index++];

        classMarker = false;
        terminated = false;
        while (index < length) {
            ch = source[index++];
            str += ch;
            if (ch === '\\') {
                ch = source[index++];
                if (isLineTerminator(ch.charCodeAt(0))) {
                    throwUnexpectedToken(null, Messages.UnterminatedRegExp);
                }
                str += ch;
            } else if (isLineTerminator(ch.charCodeAt(0))) {
                throwUnexpectedToken(null, Messages.UnterminatedRegExp);
            } else if (classMarker) {
                if (ch === ']') {
                    classMarker = false;
                }
            } else {
                if (ch === '/') {
                    terminated = true;
                    break;
                } else if (ch === '[') {
                    classMarker = true;
                }
            }
        }

        if (!terminated) {
            throwUnexpectedToken(null, Messages.UnterminatedRegExp);
        }

        body = str.substr(1, str.length - 2);
        return {
            value: body,
            literal: str
        };
    }

    function scanRegExpFlags() {
        var ch, str, flags, restore;

        str = '';
        flags = '';
        while (index < length) {
            ch = source[index];
            if (!isIdentifierPart(ch.charCodeAt(0))) {
                break;
            }

            ++index;
            if (ch === '\\' && index < length) {
                ch = source[index];
                if (ch === 'u') {
                    ++index;
                    restore = index;
                    ch = scanHexEscape('u');
                    if (ch) {
                        flags += ch;
                        for (str += '\\u'; restore < index; ++restore) {
                            str += source[restore];
                        }
                    } else {
                        index = restore;
                        flags += 'u';
                        str += '\\u';
                    }
                    tolerateUnexpectedToken();
                } else {
                    str += '\\';
                    tolerateUnexpectedToken();
                }
            } else {
                flags += ch;
                str += ch;
            }
        }

        return {
            value: flags,
            literal: str
        };
    }

    function scanRegExp() {
        var start, body, flags, value;
        scanning = true;

        lookahead = null;
        skipComment();
        start = index;

        body = scanRegExpBody();
        flags = scanRegExpFlags();
        value = testRegExp(body.value, flags.value);
        scanning = false;
        if (extra.tokenize) {
            return {
                type: Token.RegularExpression,
                value: value,
                regex: {
                    pattern: body.value,
                    flags: flags.value
                },
                lineNumber: lineNumber,
                lineStart: lineStart,
                start: start,
                end: index
            };
        }

        return {
            literal: body.literal + flags.literal,
            value: value,
            regex: {
                pattern: body.value,
                flags: flags.value
            },
            start: start,
            end: index
        };
    }

    function collectRegex() {
        var pos, loc, regex, token;

        skipComment();

        pos = index;
        loc = {
            start: {
                line: lineNumber,
                column: index - lineStart
            }
        };

        regex = scanRegExp();

        loc.end = {
            line: lineNumber,
            column: index - lineStart
        };

        if (!extra.tokenize) {
            if (extra.tokens.length > 0) {
                token = extra.tokens[extra.tokens.length - 1];
                if (token.range[0] === pos && token.type === 'Punctuator') {
                    if (token.value === '/' || token.value === '/=') {
                        extra.tokens.pop();
                    }
                }
            }

            extra.tokens.push({
                type: 'RegularExpression',
                value: regex.literal,
                regex: regex.regex,
                range: [pos, index],
                loc: loc
            });
        }

        return regex;
    }

    function isIdentifierName(token) {
        return token.type === Token.Identifier ||
            token.type === Token.Keyword ||
            token.type === Token.BooleanLiteral ||
            token.type === Token.NullLiteral;
    }

    function advanceSlash() {
        var prevToken,
            checkToken;
        prevToken = extra.tokens[extra.tokens.length - 1];
        if (!prevToken) {
            return collectRegex();
        }
        if (prevToken.type === 'Punctuator') {
            if (prevToken.value === ']') {
                return scanPunctuator();
            }
            if (prevToken.value === ')') {
                checkToken = extra.tokens[extra.openParenToken - 1];
                if (checkToken &&
                    checkToken.type === 'Keyword' &&
                    (checkToken.value === 'if' ||
                    checkToken.value === 'while' ||
                    checkToken.value === 'for' ||
                    checkToken.value === 'with')) {
                    return collectRegex();
                }
                return scanPunctuator();
            }
            if (prevToken.value === '}') {
                if (extra.tokens[extra.openCurlyToken - 3] &&
                    extra.tokens[extra.openCurlyToken - 3].type === 'Keyword') {
                    checkToken = extra.tokens[extra.openCurlyToken - 4];
                    if (!checkToken) {
                        return scanPunctuator();
                    }
                } else if (extra.tokens[extra.openCurlyToken - 4] &&
                    extra.tokens[extra.openCurlyToken - 4].type === 'Keyword') {
                    checkToken = extra.tokens[extra.openCurlyToken - 5];
                    if (!checkToken) {
                        return collectRegex();
                    }
                } else {
                    return scanPunctuator();
                }
                if (FnExprTokens.indexOf(checkToken.value) >= 0) {
                    return scanPunctuator();
                }
                return collectRegex();
            }
            return collectRegex();
        }
        if (prevToken.type === 'Keyword' && prevToken.value !== 'this') {
            return collectRegex();
        }
        return scanPunctuator();
    }

    function advance() {
        var cp, token;

        if (index >= length) {
            return {
                type: Token.EOF,
                lineNumber: lineNumber,
                lineStart: lineStart,
                start: index,
                end: index
            };
        }

        cp = source.charCodeAt(index);

        if (isIdentifierStart(cp)) {
            token = scanIdentifier();
            if (strict && isStrictModeReservedWord(token.value)) {
                token.type = Token.Keyword;
            }
            return token;
        }

        if (cp === 0x28 || cp === 0x29 || cp === 0x3B) {
            return scanPunctuator();
        }

        if (cp === 0x27 || cp === 0x22) {
            return scanStringLiteral();
        }

        if (cp === 0x2E) {
            if (isDecimalDigit(source.charCodeAt(index + 1))) {
                return scanNumericLiteral();
            }
            return scanPunctuator();
        }

        if (isDecimalDigit(cp)) {
            return scanNumericLiteral();
        }

        if (extra.tokenize && cp === 0x2F) {
            return advanceSlash();
        }

        if (cp === 0x60 || (cp === 0x7D && state.curlyStack[state.curlyStack.length - 1] === '${')) {
            return scanTemplate();
        }

        if (cp >= 0xD800 && cp < 0xDFFF) {
            cp = codePointAt(index);
            if (isIdentifierStart(cp)) {
                return scanIdentifier();
            }
        }

        return scanPunctuator();
    }

    function collectToken() {
        var loc, token, value, entry;

        loc = {
            start: {
                line: lineNumber,
                column: index - lineStart
            }
        };

        token = advance();
        loc.end = {
            line: lineNumber,
            column: index - lineStart
        };

        if (token.type !== Token.EOF) {
            value = source.slice(token.start, token.end);
            entry = {
                type: TokenName[token.type],
                value: value,
                range: [token.start, token.end],
                loc: loc
            };
            if (token.regex) {
                entry.regex = {
                    pattern: token.regex.pattern,
                    flags: token.regex.flags
                };
            }
            extra.tokens.push(entry);
        }

        return token;
    }

    function lex() {
        var token;
        scanning = true;

        lastIndex = index;
        lastLineNumber = lineNumber;
        lastLineStart = lineStart;

        skipComment();

        token = lookahead;

        startIndex = index;
        startLineNumber = lineNumber;
        startLineStart = lineStart;

        lookahead = (typeof extra.tokens !== 'undefined') ? collectToken() : advance();
        scanning = false;
        return token;
    }

    function peek() {
        scanning = true;

        skipComment();

        lastIndex = index;
        lastLineNumber = lineNumber;
        lastLineStart = lineStart;

        startIndex = index;
        startLineNumber = lineNumber;
        startLineStart = lineStart;

        lookahead = (typeof extra.tokens !== 'undefined') ? collectToken() : advance();
        scanning = false;
    }

    function Position() {
        this.line = startLineNumber;
        this.column = startIndex - startLineStart;
    }

    function SourceLocation() {
        this.start = new Position();
        this.end = null;
    }

    function WrappingSourceLocation(startToken) {
        this.start = {
            line: startToken.lineNumber,
            column: startToken.start - startToken.lineStart
        };
        this.end = null;
    }

    function Node() {
        if (extra.range) {
            this.range = [startIndex, 0];
        }
        if (extra.loc) {
            this.loc = new SourceLocation();
        }
    }

    function WrappingNode(startToken) {
        if (extra.range) {
            this.range = [startToken.start, 0];
        }
        if (extra.loc) {
            this.loc = new WrappingSourceLocation(startToken);
        }
    }

    WrappingNode.prototype = Node.prototype = {

        processComment: function () {
            var lastChild,
                leadingComments,
                trailingComments,
                bottomRight = extra.bottomRightStack,
                i,
                comment,
                last = bottomRight[bottomRight.length - 1];

            if (this.type === Syntax.Program) {
                if (this.body.length > 0) {
                    return;
                }
            }

            if (extra.trailingComments.length > 0) {
                trailingComments = [];
                for (i = extra.trailingComments.length - 1; i >= 0; --i) {
                    comment = extra.trailingComments[i];
                    if (comment.range[0] >= this.range[1]) {
                        trailingComments.unshift(comment);
                        extra.trailingComments.splice(i, 1);
                    }
                }
                extra.trailingComments = [];
            } else {
                if (last && last.trailingComments && last.trailingComments[0].range[0] >= this.range[1]) {
                    trailingComments = last.trailingComments;
                    delete last.trailingComments;
                }
            }

            while (last && last.range[0] >= this.range[0]) {
                lastChild = bottomRight.pop();
                last = bottomRight[bottomRight.length - 1];
            }

            if (lastChild) {
                if (lastChild.leadingComments) {
                    leadingComments = [];
                    for (i = lastChild.leadingComments.length - 1; i >= 0; --i) {
                        comment = lastChild.leadingComments[i];
                        if (comment.range[1] <= this.range[0]) {
                            leadingComments.unshift(comment);
                            lastChild.leadingComments.splice(i, 1);
                        }
                    }

                    if (!lastChild.leadingComments.length) {
                        lastChild.leadingComments = undefined;
                    }
                }
            } else if (extra.leadingComments.length > 0) {
                leadingComments = [];
                for (i = extra.leadingComments.length - 1; i >= 0; --i) {
                    comment = extra.leadingComments[i];
                    if (comment.range[1] <= this.range[0]) {
                        leadingComments.unshift(comment);
                        extra.leadingComments.splice(i, 1);
                    }
                }
            }


            if (leadingComments && leadingComments.length > 0) {
                this.leadingComments = leadingComments;
            }
            if (trailingComments && trailingComments.length > 0) {
                this.trailingComments = trailingComments;
            }

            bottomRight.push(this);
        },

        finish: function () {
            if (extra.range) {
                this.range[1] = lastIndex;
            }
            if (extra.loc) {
                this.loc.end = {
                    line: lastLineNumber,
                    column: lastIndex - lastLineStart
                };
                if (extra.source) {
                    this.loc.source = extra.source;
                }
            }

            if (extra.attachComment) {
                this.processComment();
            }
        },

        finishArrayExpression: function (elements) {
            this.type = Syntax.ArrayExpression;
            this.elements = elements;
            this.finish();
            return this;
        },

        finishArrayPattern: function (elements) {
            this.type = Syntax.ArrayPattern;
            this.elements = elements;
            this.finish();
            return this;
        },

        finishArrowFunctionExpression: function (params, defaults, body, expression) {
            this.type = Syntax.ArrowFunctionExpression;
            this.id = null;
            this.params = params;
            this.defaults = defaults;
            this.body = body;
            this.generator = false;
            this.expression = expression;
            this.finish();
            return this;
        },

        finishAssignmentExpression: function (operator, left, right) {
            this.type = Syntax.AssignmentExpression;
            this.operator = operator;
            this.left = left;
            this.right = right;
            this.finish();
            return this;
        },

        finishAssignmentPattern: function (left, right) {
            this.type = Syntax.AssignmentPattern;
            this.left = left;
            this.right = right;
            this.finish();
            return this;
        },

        finishBinaryExpression: function (operator, left, right) {
            this.type = (operator === '||' || operator === '&&') ? Syntax.LogicalExpression : Syntax.BinaryExpression;
            this.operator = operator;
            this.left = left;
            this.right = right;
            this.finish();
            return this;
        },

        finishBlockStatement: function (body) {
            this.type = Syntax.BlockStatement;
            this.body = body;
            this.finish();
            return this;
        },

        finishBreakStatement: function (label) {
            this.type = Syntax.BreakStatement;
            this.label = label;
            this.finish();
            return this;
        },

        finishCallExpression: function (callee, args) {
            this.type = Syntax.CallExpression;
            this.callee = callee;
            this.arguments = args;
            this.finish();
            return this;
        },

        finishCatchClause: function (param, body) {
            this.type = Syntax.CatchClause;
            this.param = param;
            this.body = body;
            this.finish();
            return this;
        },

        finishClassBody: function (body) {
            this.type = Syntax.ClassBody;
            this.body = body;
            this.finish();
            return this;
        },

        finishClassDeclaration: function (id, superClass, body) {
            this.type = Syntax.ClassDeclaration;
            this.id = id;
            this.superClass = superClass;
            this.body = body;
            this.finish();
            return this;
        },

        finishClassExpression: function (id, superClass, body) {
            this.type = Syntax.ClassExpression;
            this.id = id;
            this.superClass = superClass;
            this.body = body;
            this.finish();
            return this;
        },

        finishConditionalExpression: function (test, consequent, alternate) {
            this.type = Syntax.ConditionalExpression;
            this.test = test;
            this.consequent = consequent;
            this.alternate = alternate;
            this.finish();
            return this;
        },

        finishContinueStatement: function (label) {
            this.type = Syntax.ContinueStatement;
            this.label = label;
            this.finish();
            return this;
        },

        finishDebuggerStatement: function () {
            this.type = Syntax.DebuggerStatement;
            this.finish();
            return this;
        },

        finishDoWhileStatement: function (body, test) {
            this.type = Syntax.DoWhileStatement;
            this.body = body;
            this.test = test;
            this.finish();
            return this;
        },

        finishEmptyStatement: function () {
            this.type = Syntax.EmptyStatement;
            this.finish();
            return this;
        },

        finishExpressionStatement: function (expression) {
            this.type = Syntax.ExpressionStatement;
            this.expression = expression;
            this.finish();
            return this;
        },

        finishForStatement: function (init, test, update, body) {
            this.type = Syntax.ForStatement;
            this.init = init;
            this.test = test;
            this.update = update;
            this.body = body;
            this.finish();
            return this;
        },

        finishForOfStatement: function (left, right, body) {
            this.type = Syntax.ForOfStatement;
            this.left = left;
            this.right = right;
            this.body = body;
            this.finish();
            return this;
        },

        finishForInStatement: function (left, right, body) {
            this.type = Syntax.ForInStatement;
            this.left = left;
            this.right = right;
            this.body = body;
            this.each = false;
            this.finish();
            return this;
        },

        finishFunctionDeclaration: function (id, params, defaults, body, generator) {
            this.type = Syntax.FunctionDeclaration;
            this.id = id;
            this.params = params;
            this.defaults = defaults;
            this.body = body;
            this.generator = generator;
            this.expression = false;
            this.finish();
            return this;
        },

        finishFunctionExpression: function (id, params, defaults, body, generator) {
            this.type = Syntax.FunctionExpression;
            this.id = id;
            this.params = params;
            this.defaults = defaults;
            this.body = body;
            this.generator = generator;
            this.expression = false;
            this.finish();
            return this;
        },

        finishIdentifier: function (name) {
            this.type = Syntax.Identifier;
            this.name = name;
            this.finish();
            return this;
        },

        finishIfStatement: function (test, consequent, alternate) {
            this.type = Syntax.IfStatement;
            this.test = test;
            this.consequent = consequent;
            this.alternate = alternate;
            this.finish();
            return this;
        },

        finishLabeledStatement: function (label, body) {
            this.type = Syntax.LabeledStatement;
            this.label = label;
            this.body = body;
            this.finish();
            return this;
        },

        finishLiteral: function (token) {
            this.type = Syntax.Literal;
            this.value = token.value;
            this.raw = source.slice(token.start, token.end);
            if (token.regex) {
                this.regex = token.regex;
            }
            this.finish();
            return this;
        },

        finishMemberExpression: function (accessor, object, property) {
            this.type = Syntax.MemberExpression;
            this.computed = accessor === '[';
            this.object = object;
            this.property = property;
            this.finish();
            return this;
        },

        finishMetaProperty: function (meta, property) {
            this.type = Syntax.MetaProperty;
            this.meta = meta;
            this.property = property;
            this.finish();
            return this;
        },

        finishNewExpression: function (callee, args) {
            this.type = Syntax.NewExpression;
            this.callee = callee;
            this.arguments = args;
            this.finish();
            return this;
        },

        finishObjectExpression: function (properties) {
            this.type = Syntax.ObjectExpression;
            this.properties = properties;
            this.finish();
            return this;
        },

        finishObjectPattern: function (properties) {
            this.type = Syntax.ObjectPattern;
            this.properties = properties;
            this.finish();
            return this;
        },

        finishPostfixExpression: function (operator, argument) {
            this.type = Syntax.UpdateExpression;
            this.operator = operator;
            this.argument = argument;
            this.prefix = false;
            this.finish();
            return this;
        },

        finishProgram: function (body, sourceType) {
            this.type = Syntax.Program;
            this.body = body;
            this.sourceType = sourceType;
            this.finish();
            return this;
        },

        finishProperty: function (kind, key, computed, value, method, shorthand) {
            this.type = Syntax.Property;
            this.key = key;
            this.computed = computed;
            this.value = value;
            this.kind = kind;
            this.method = method;
            this.shorthand = shorthand;
            this.finish();
            return this;
        },

        finishRestElement: function (argument) {
            this.type = Syntax.RestElement;
            this.argument = argument;
            this.finish();
            return this;
        },

        finishReturnStatement: function (argument) {
            this.type = Syntax.ReturnStatement;
            this.argument = argument;
            this.finish();
            return this;
        },

        finishSequenceExpression: function (expressions) {
            this.type = Syntax.SequenceExpression;
            this.expressions = expressions;
            this.finish();
            return this;
        },

        finishSpreadElement: function (argument) {
            this.type = Syntax.SpreadElement;
            this.argument = argument;
            this.finish();
            return this;
        },

        finishSwitchCase: function (test, consequent) {
            this.type = Syntax.SwitchCase;
            this.test = test;
            this.consequent = consequent;
            this.finish();
            return this;
        },

        finishSuper: function () {
            this.type = Syntax.Super;
            this.finish();
            return this;
        },

        finishSwitchStatement: function (discriminant, cases) {
            this.type = Syntax.SwitchStatement;
            this.discriminant = discriminant;
            this.cases = cases;
            this.finish();
            return this;
        },

        finishTaggedTemplateExpression: function (tag, quasi) {
            this.type = Syntax.TaggedTemplateExpression;
            this.tag = tag;
            this.quasi = quasi;
            this.finish();
            return this;
        },

        finishTemplateElement: function (value, tail) {
            this.type = Syntax.TemplateElement;
            this.value = value;
            this.tail = tail;
            this.finish();
            return this;
        },

        finishTemplateLiteral: function (quasis, expressions) {
            this.type = Syntax.TemplateLiteral;
            this.quasis = quasis;
            this.expressions = expressions;
            this.finish();
            return this;
        },

        finishThisExpression: function () {
            this.type = Syntax.ThisExpression;
            this.finish();
            return this;
        },

        finishThrowStatement: function (argument) {
            this.type = Syntax.ThrowStatement;
            this.argument = argument;
            this.finish();
            return this;
        },

        finishTryStatement: function (block, handler, finalizer) {
            this.type = Syntax.TryStatement;
            this.block = block;
            this.guardedHandlers = [];
            this.handlers = handler ? [handler] : [];
            this.handler = handler;
            this.finalizer = finalizer;
            this.finish();
            return this;
        },

        finishUnaryExpression: function (operator, argument) {
            this.type = (operator === '++' || operator === '--') ? Syntax.UpdateExpression : Syntax.UnaryExpression;
            this.operator = operator;
            this.argument = argument;
            this.prefix = true;
            this.finish();
            return this;
        },

        finishVariableDeclaration: function (declarations) {
            this.type = Syntax.VariableDeclaration;
            this.declarations = declarations;
            this.kind = 'var';
            this.finish();
            return this;
        },

        finishLexicalDeclaration: function (declarations, kind) {
            this.type = Syntax.VariableDeclaration;
            this.declarations = declarations;
            this.kind = kind;
            this.finish();
            return this;
        },

        finishVariableDeclarator: function (id, init) {
            this.type = Syntax.VariableDeclarator;
            this.id = id;
            this.init = init;
            this.finish();
            return this;
        },

        finishWhileStatement: function (test, body) {
            this.type = Syntax.WhileStatement;
            this.test = test;
            this.body = body;
            this.finish();
            return this;
        },

        finishWithStatement: function (object, body) {
            this.type = Syntax.WithStatement;
            this.object = object;
            this.body = body;
            this.finish();
            return this;
        },

        finishExportSpecifier: function (local, exported) {
            this.type = Syntax.ExportSpecifier;
            this.exported = exported || local;
            this.local = local;
            this.finish();
            return this;
        },

        finishImportDefaultSpecifier: function (local) {
            this.type = Syntax.ImportDefaultSpecifier;
            this.local = local;
            this.finish();
            return this;
        },

        finishImportNamespaceSpecifier: function (local) {
            this.type = Syntax.ImportNamespaceSpecifier;
            this.local = local;
            this.finish();
            return this;
        },

        finishExportNamedDeclaration: function (declaration, specifiers, src) {
            this.type = Syntax.ExportNamedDeclaration;
            this.declaration = declaration;
            this.specifiers = specifiers;
            this.source = src;
            this.finish();
            return this;
        },

        finishExportDefaultDeclaration: function (declaration) {
            this.type = Syntax.ExportDefaultDeclaration;
            this.declaration = declaration;
            this.finish();
            return this;
        },

        finishExportAllDeclaration: function (src) {
            this.type = Syntax.ExportAllDeclaration;
            this.source = src;
            this.finish();
            return this;
        },

        finishImportSpecifier: function (local, imported) {
            this.type = Syntax.ImportSpecifier;
            this.local = local || imported;
            this.imported = imported;
            this.finish();
            return this;
        },

        finishImportDeclaration: function (specifiers, src) {
            this.type = Syntax.ImportDeclaration;
            this.specifiers = specifiers;
            this.source = src;
            this.finish();
            return this;
        },

        finishYieldExpression: function (argument, delegate) {
            this.type = Syntax.YieldExpression;
            this.argument = argument;
            this.delegate = delegate;
            this.finish();
            return this;
        }
    };


    function recordError(error) {
        var e, existing;

        for (e = 0; e < extra.errors.length; e++) {
            existing = extra.errors[e];
            if (existing.index === error.index && existing.message === error.message) {
                return;
            }
        }

        extra.errors.push(error);
    }

    function constructError(msg, column) {
        var error = new Error(msg);
        try {
            throw error;
        } catch (base) {
            if (Object.create && Object.defineProperty) {
                error = Object.create(base);
                Object.defineProperty(error, 'column', { value: column });
            }
        } finally {
            return error;
        }
    }

    function createError(line, pos, description) {
        var msg, column, error;

        msg = 'Line ' + line + ': ' + description;
        column = pos - (scanning ? lineStart : lastLineStart) + 1;
        error = constructError(msg, column);
        error.lineNumber = line;
        error.description = description;
        error.index = pos;
        return error;
    }

    function throwError(messageFormat) {
        var args, msg;

        args = Array.prototype.slice.call(arguments, 1);
        msg = messageFormat.replace(/%(\d)/g,
            function (whole, idx) {
                assert(idx < args.length, 'Message reference must be in range');
                return args[idx];
            }
        );

        throw createError(lastLineNumber, lastIndex, msg);
    }

    function tolerateError(messageFormat) {
        var args, msg, error;

        args = Array.prototype.slice.call(arguments, 1);
        msg = messageFormat.replace(/%(\d)/g,
            function (whole, idx) {
                assert(idx < args.length, 'Message reference must be in range');
                return args[idx];
            }
        );

        error = createError(lineNumber, lastIndex, msg);
        if (extra.errors) {
            recordError(error);
        } else {
            throw error;
        }
    }


    function unexpectedTokenError(token, message) {
        var value, msg = message || Messages.UnexpectedToken;

        if (token) {
            if (!message) {
                msg = (token.type === Token.EOF) ? Messages.UnexpectedEOS :
                    (token.type === Token.Identifier) ? Messages.UnexpectedIdentifier :
                        (token.type === Token.NumericLiteral) ? Messages.UnexpectedNumber :
                            (token.type === Token.StringLiteral) ? Messages.UnexpectedString :
                                (token.type === Token.Template) ? Messages.UnexpectedTemplate :
                                    Messages.UnexpectedToken;

                if (token.type === Token.Keyword) {
                    if (isFutureReservedWord(token.value)) {
                        msg = Messages.UnexpectedReserved;
                    } else if (strict && isStrictModeReservedWord(token.value)) {
                        msg = Messages.StrictReservedWord;
                    }
                }
            }

            value = (token.type === Token.Template) ? token.value.raw : token.value;
        } else {
            value = 'ILLEGAL';
        }

        msg = msg.replace('%0', value);

        return (token && typeof token.lineNumber === 'number') ?
            createError(token.lineNumber, token.start, msg) :
            createError(scanning ? lineNumber : lastLineNumber, scanning ? index : lastIndex, msg);
    }

    function throwUnexpectedToken(token, message) {
        throw unexpectedTokenError(token, message);
    }

    function tolerateUnexpectedToken(token, message) {
        var error = unexpectedTokenError(token, message);
        if (extra.errors) {
            recordError(error);
        } else {
            throw error;
        }
    }


    function expect(value) {
        var token = lex();
        if (token.type !== Token.Punctuator || token.value !== value) {
            throwUnexpectedToken(token);
        }
    }

    function expectCommaSeparator() {
        var token;

        if (extra.errors) {
            token = lookahead;
            if (token.type === Token.Punctuator && token.value === ',') {
                lex();
            } else if (token.type === Token.Punctuator && token.value === ';') {
                lex();
                tolerateUnexpectedToken(token);
            } else {
                tolerateUnexpectedToken(token, Messages.UnexpectedToken);
            }
        } else {
            expect(',');
        }
    }


    function expectKeyword(keyword) {
        var token = lex();
        if (token.type !== Token.Keyword || token.value !== keyword) {
            throwUnexpectedToken(token);
        }
    }


    function match(value) {
        return lookahead.type === Token.Punctuator && lookahead.value === value;
    }


    function matchKeyword(keyword) {
        return lookahead.type === Token.Keyword && lookahead.value === keyword;
    }


    function matchContextualKeyword(keyword) {
        return lookahead.type === Token.Identifier && lookahead.value === keyword;
    }


    function matchAssign() {
        var op;

        if (lookahead.type !== Token.Punctuator) {
            return false;
        }
        op = lookahead.value;
        return op === '=' ||
            op === '*=' ||
            op === '/=' ||
            op === '%=' ||
            op === '+=' ||
            op === '-=' ||
            op === '<<=' ||
            op === '>>=' ||
            op === '>>>=' ||
            op === '&=' ||
            op === '^=' ||
            op === '|=';
    }

    function consumeSemicolon() {
        if (source.charCodeAt(startIndex) === 0x3B || match(';')) {
            lex();
            return;
        }

        if (hasLineTerminator) {
            return;
        }

        lastIndex = startIndex;
        lastLineNumber = startLineNumber;
        lastLineStart = startLineStart;

        if (lookahead.type !== Token.EOF && !match('}')) {
            throwUnexpectedToken(lookahead);
        }
    }
    function isolateCoverGrammar(parser) {
        var oldIsBindingElement = isBindingElement,
            oldIsAssignmentTarget = isAssignmentTarget,
            oldFirstCoverInitializedNameError = firstCoverInitializedNameError,
            result;
        isBindingElement = true;
        isAssignmentTarget = true;
        firstCoverInitializedNameError = null;
        result = parser();
        if (firstCoverInitializedNameError !== null) {
            throwUnexpectedToken(firstCoverInitializedNameError);
        }
        isBindingElement = oldIsBindingElement;
        isAssignmentTarget = oldIsAssignmentTarget;
        firstCoverInitializedNameError = oldFirstCoverInitializedNameError;
        return result;
    }

    function inheritCoverGrammar(parser) {
        var oldIsBindingElement = isBindingElement,
            oldIsAssignmentTarget = isAssignmentTarget,
            oldFirstCoverInitializedNameError = firstCoverInitializedNameError,
            result;
        isBindingElement = true;
        isAssignmentTarget = true;
        firstCoverInitializedNameError = null;
        result = parser();
        isBindingElement = isBindingElement && oldIsBindingElement;
        isAssignmentTarget = isAssignmentTarget && oldIsAssignmentTarget;
        firstCoverInitializedNameError = oldFirstCoverInitializedNameError || firstCoverInitializedNameError;
        return result;
    }


    function parseArrayPattern(params, kind) {
        var node = new Node(), elements = [], rest, restNode;
        expect('[');

        while (!match(']')) {
            if (match(',')) {
                lex();
                elements.push(null);
            } else {
                if (match('...')) {
                    restNode = new Node();
                    lex();
                    params.push(lookahead);
                    rest = parseVariableIdentifier(kind);
                    elements.push(restNode.finishRestElement(rest));
                    break;
                } else {
                    elements.push(parsePatternWithDefault(params, kind));
                }
                if (!match(']')) {
                    expect(',');
                }
            }

        }

        expect(']');

        return node.finishArrayPattern(elements);
    }

    function parsePropertyPattern(params, kind) {
        var node = new Node(), key, keyToken, computed = match('['), init;
        if (lookahead.type === Token.Identifier) {
            keyToken = lookahead;
            key = parseVariableIdentifier();
            if (match('=')) {
                params.push(keyToken);
                lex();
                init = parseAssignmentExpression();

                return node.finishProperty(
                    'init', key, false,
                    new WrappingNode(keyToken).finishAssignmentPattern(key, init), false, false);
            } else if (!match(':')) {
                params.push(keyToken);
                return node.finishProperty('init', key, false, key, false, true);
            }
        } else {
            key = parseObjectPropertyKey();
        }
        expect(':');
        init = parsePatternWithDefault(params, kind);
        return node.finishProperty('init', key, computed, init, false, false);
    }

    function parseObjectPattern(params, kind) {
        var node = new Node(), properties = [];

        expect('{');

        while (!match('}')) {
            properties.push(parsePropertyPattern(params, kind));
            if (!match('}')) {
                expect(',');
            }
        }

        lex();

        return node.finishObjectPattern(properties);
    }

    function parsePattern(params, kind) {
        if (match('[')) {
            return parseArrayPattern(params, kind);
        } else if (match('{')) {
            return parseObjectPattern(params, kind);
        } else if (matchKeyword('let')) {
            if (kind === 'const' || kind === 'let') {
                tolerateUnexpectedToken(lookahead, Messages.UnexpectedToken);
            }
        }

        params.push(lookahead);
        return parseVariableIdentifier(kind);
    }

    function parsePatternWithDefault(params, kind) {
        var startToken = lookahead, pattern, previousAllowYield, right;
        pattern = parsePattern(params, kind);
        if (match('=')) {
            lex();
            previousAllowYield = state.allowYield;
            state.allowYield = true;
            right = isolateCoverGrammar(parseAssignmentExpression);
            state.allowYield = previousAllowYield;
            pattern = new WrappingNode(startToken).finishAssignmentPattern(pattern, right);
        }
        return pattern;
    }


    function parseArrayInitializer() {
        var elements = [], node = new Node(), restSpread;

        expect('[');

        while (!match(']')) {
            if (match(',')) {
                lex();
                elements.push(null);
            } else if (match('...')) {
                restSpread = new Node();
                lex();
                restSpread.finishSpreadElement(inheritCoverGrammar(parseAssignmentExpression));

                if (!match(']')) {
                    isAssignmentTarget = isBindingElement = false;
                    expect(',');
                }
                elements.push(restSpread);
            } else {
                elements.push(inheritCoverGrammar(parseAssignmentExpression));

                if (!match(']')) {
                    expect(',');
                }
            }
        }

        lex();

        return node.finishArrayExpression(elements);
    }


    function parsePropertyFunction(node, paramInfo, isGenerator) {
        var previousStrict, body;

        isAssignmentTarget = isBindingElement = false;

        previousStrict = strict;
        body = isolateCoverGrammar(parseFunctionSourceElements);

        if (strict && paramInfo.firstRestricted) {
            tolerateUnexpectedToken(paramInfo.firstRestricted, paramInfo.message);
        }
        if (strict && paramInfo.stricted) {
            tolerateUnexpectedToken(paramInfo.stricted, paramInfo.message);
        }

        strict = previousStrict;
        return node.finishFunctionExpression(null, paramInfo.params, paramInfo.defaults, body, isGenerator);
    }

    function parsePropertyMethodFunction() {
        var params, method, node = new Node(),
            previousAllowYield = state.allowYield;

        state.allowYield = false;
        params = parseParams();
        state.allowYield = previousAllowYield;

        state.allowYield = false;
        method = parsePropertyFunction(node, params, false);
        state.allowYield = previousAllowYield;

        return method;
    }

    function parseObjectPropertyKey() {
        var token, node = new Node(), expr;

        token = lex();


        switch (token.type) {
            case Token.StringLiteral:
            case Token.NumericLiteral:
                if (strict && token.octal) {
                    tolerateUnexpectedToken(token, Messages.StrictOctalLiteral);
                }
                return node.finishLiteral(token);
            case Token.Identifier:
            case Token.BooleanLiteral:
            case Token.NullLiteral:
            case Token.Keyword:
                return node.finishIdentifier(token.value);
            case Token.Punctuator:
                if (token.value === '[') {
                    expr = isolateCoverGrammar(parseAssignmentExpression);
                    expect(']');
                    return expr;
                }
                break;
        }
        throwUnexpectedToken(token);
    }

    function lookaheadPropertyName() {
        switch (lookahead.type) {
            case Token.Identifier:
            case Token.StringLiteral:
            case Token.BooleanLiteral:
            case Token.NullLiteral:
            case Token.NumericLiteral:
            case Token.Keyword:
                return true;
            case Token.Punctuator:
                return lookahead.value === '[';
        }
        return false;
    }

    function tryParseMethodDefinition(token, key, computed, node) {
        var value, options, methodNode, params,
            previousAllowYield = state.allowYield;

        if (token.type === Token.Identifier) {

            if (token.value === 'get' && lookaheadPropertyName()) {
                computed = match('[');
                key = parseObjectPropertyKey();
                methodNode = new Node();
                expect('(');
                expect(')');

                state.allowYield = false;
                value = parsePropertyFunction(methodNode, {
                    params: [],
                    defaults: [],
                    stricted: null,
                    firstRestricted: null,
                    message: null
                }, false);
                state.allowYield = previousAllowYield;

                return node.finishProperty('get', key, computed, value, false, false);
            } else if (token.value === 'set' && lookaheadPropertyName()) {
                computed = match('[');
                key = parseObjectPropertyKey();
                methodNode = new Node();
                expect('(');

                options = {
                    params: [],
                    defaultCount: 0,
                    defaults: [],
                    firstRestricted: null,
                    paramSet: {}
                };
                if (match(')')) {
                    tolerateUnexpectedToken(lookahead);
                } else {
                    state.allowYield = false;
                    parseParam(options);
                    state.allowYield = previousAllowYield;
                    if (options.defaultCount === 0) {
                        options.defaults = [];
                    }
                }
                expect(')');

                state.allowYield = false;
                value = parsePropertyFunction(methodNode, options, false);
                state.allowYield = previousAllowYield;

                return node.finishProperty('set', key, computed, value, false, false);
            }
        } else if (token.type === Token.Punctuator && token.value === '*' && lookaheadPropertyName()) {
            computed = match('[');
            key = parseObjectPropertyKey();
            methodNode = new Node();

            state.allowYield = true;
            params = parseParams();
            state.allowYield = previousAllowYield;

            state.allowYield = false;
            value = parsePropertyFunction(methodNode, params, true);
            state.allowYield = previousAllowYield;

            return node.finishProperty('init', key, computed, value, true, false);
        }

        if (key && match('(')) {
            value = parsePropertyMethodFunction();
            return node.finishProperty('init', key, computed, value, true, false);
        }

        return null;
    }

    function parseObjectProperty(hasProto) {
        var token = lookahead, node = new Node(), computed, key, maybeMethod, proto, value;

        computed = match('[');
        if (match('*')) {
            lex();
        } else {
            key = parseObjectPropertyKey();
        }
        maybeMethod = tryParseMethodDefinition(token, key, computed, node);
        if (maybeMethod) {
            return maybeMethod;
        }

        if (!key) {
            throwUnexpectedToken(lookahead);
        }

        if (!computed) {
            proto = (key.type === Syntax.Identifier && key.name === '__proto__') ||
            (key.type === Syntax.Literal && key.value === '__proto__');
            if (hasProto.value && proto) {
                tolerateError(Messages.DuplicateProtoProperty);
            }
            hasProto.value |= proto;
        }

        if (match(':')) {
            lex();
            value = inheritCoverGrammar(parseAssignmentExpression);
            return node.finishProperty('init', key, computed, value, false, false);
        }

        if (token.type === Token.Identifier) {
            if (match('=')) {
                firstCoverInitializedNameError = lookahead;
                lex();
                value = isolateCoverGrammar(parseAssignmentExpression);
                return node.finishProperty('init', key, computed,
                    new WrappingNode(token).finishAssignmentPattern(key, value), false, true);
            }
            return node.finishProperty('init', key, computed, key, false, true);
        }

        throwUnexpectedToken(lookahead);
    }

    function parseObjectInitializer() {
        var properties = [], hasProto = {value: false}, node = new Node();

        expect('{');

        while (!match('}')) {
            properties.push(parseObjectProperty(hasProto));

            if (!match('}')) {
                expectCommaSeparator();
            }
        }

        expect('}');

        return node.finishObjectExpression(properties);
    }

    function reinterpretExpressionAsPattern(expr) {
        var i;
        switch (expr.type) {
            case Syntax.Identifier:
            case Syntax.MemberExpression:
            case Syntax.RestElement:
            case Syntax.AssignmentPattern:
                break;
            case Syntax.SpreadElement:
                expr.type = Syntax.RestElement;
                reinterpretExpressionAsPattern(expr.argument);
                break;
            case Syntax.ArrayExpression:
                expr.type = Syntax.ArrayPattern;
                for (i = 0; i < expr.elements.length; i++) {
                    if (expr.elements[i] !== null) {
                        reinterpretExpressionAsPattern(expr.elements[i]);
                    }
                }
                break;
            case Syntax.ObjectExpression:
                expr.type = Syntax.ObjectPattern;
                for (i = 0; i < expr.properties.length; i++) {
                    reinterpretExpressionAsPattern(expr.properties[i].value);
                }
                break;
            case Syntax.AssignmentExpression:
                expr.type = Syntax.AssignmentPattern;
                reinterpretExpressionAsPattern(expr.left);
                break;
            default:
                break;
        }
    }


    function parseTemplateElement(option) {
        var node, token;

        if (lookahead.type !== Token.Template || (option.head && !lookahead.head)) {
            throwUnexpectedToken();
        }

        node = new Node();
        token = lex();

        return node.finishTemplateElement({ raw: token.value.raw, cooked: token.value.cooked }, token.tail);
    }

    function parseTemplateLiteral() {
        var quasi, quasis, expressions, node = new Node();

        quasi = parseTemplateElement({ head: true });
        quasis = [quasi];
        expressions = [];

        while (!quasi.tail) {
            expressions.push(parseExpression());
            quasi = parseTemplateElement({ head: false });
            quasis.push(quasi);
        }

        return node.finishTemplateLiteral(quasis, expressions);
    }


    function parseGroupExpression() {
        var expr, expressions, startToken, i, params = [];

        expect('(');

        if (match(')')) {
            lex();
            if (!match('=>')) {
                expect('=>');
            }
            return {
                type: PlaceHolders.ArrowParameterPlaceHolder,
                params: [],
                rawParams: []
            };
        }

        startToken = lookahead;
        if (match('...')) {
            expr = parseRestElement(params);
            expect(')');
            if (!match('=>')) {
                expect('=>');
            }
            return {
                type: PlaceHolders.ArrowParameterPlaceHolder,
                params: [expr]
            };
        }

        isBindingElement = true;
        expr = inheritCoverGrammar(parseAssignmentExpression);

        if (match(',')) {
            isAssignmentTarget = false;
            expressions = [expr];

            while (startIndex < length) {
                if (!match(',')) {
                    break;
                }
                lex();

                if (match('...')) {
                    if (!isBindingElement) {
                        throwUnexpectedToken(lookahead);
                    }
                    expressions.push(parseRestElement(params));
                    expect(')');
                    if (!match('=>')) {
                        expect('=>');
                    }
                    isBindingElement = false;
                    for (i = 0; i < expressions.length; i++) {
                        reinterpretExpressionAsPattern(expressions[i]);
                    }
                    return {
                        type: PlaceHolders.ArrowParameterPlaceHolder,
                        params: expressions
                    };
                }

                expressions.push(inheritCoverGrammar(parseAssignmentExpression));
            }

            expr = new WrappingNode(startToken).finishSequenceExpression(expressions);
        }


        expect(')');

        if (match('=>')) {
            if (expr.type === Syntax.Identifier && expr.name === 'yield') {
                return {
                    type: PlaceHolders.ArrowParameterPlaceHolder,
                    params: [expr]
                };
            }

            if (!isBindingElement) {
                throwUnexpectedToken(lookahead);
            }

            if (expr.type === Syntax.SequenceExpression) {
                for (i = 0; i < expr.expressions.length; i++) {
                    reinterpretExpressionAsPattern(expr.expressions[i]);
                }
            } else {
                reinterpretExpressionAsPattern(expr);
            }

            expr = {
                type: PlaceHolders.ArrowParameterPlaceHolder,
                params: expr.type === Syntax.SequenceExpression ? expr.expressions : [expr]
            };
        }
        isBindingElement = false;
        return expr;
    }


    function parsePrimaryExpression() {
        var type, token, expr, node;

        if (match('(')) {
            isBindingElement = false;
            return inheritCoverGrammar(parseGroupExpression);
        }

        if (match('[')) {
            return inheritCoverGrammar(parseArrayInitializer);
        }

        if (match('{')) {
            return inheritCoverGrammar(parseObjectInitializer);
        }

        type = lookahead.type;
        node = new Node();

        if (type === Token.Identifier) {
            if (state.sourceType === 'module' && lookahead.value === 'await') {
                tolerateUnexpectedToken(lookahead);
            }
            expr = node.finishIdentifier(lex().value);
        } else if (type === Token.StringLiteral || type === Token.NumericLiteral) {
            isAssignmentTarget = isBindingElement = false;
            if (strict && lookahead.octal) {
                tolerateUnexpectedToken(lookahead, Messages.StrictOctalLiteral);
            }
            expr = node.finishLiteral(lex());
        } else if (type === Token.Keyword) {
            if (!strict && state.allowYield && matchKeyword('yield')) {
                return parseNonComputedProperty();
            }
            isAssignmentTarget = isBindingElement = false;
            if (matchKeyword('function')) {
                return parseFunctionExpression();
            }
            if (matchKeyword('this')) {
                lex();
                return node.finishThisExpression();
            }
            if (matchKeyword('class')) {
                return parseClassExpression();
            }
            if (!strict && matchKeyword('let')) {
                return node.finishIdentifier(lex().value);
            }
            throwUnexpectedToken(lex());
        } else if (type === Token.BooleanLiteral) {
            isAssignmentTarget = isBindingElement = false;
            token = lex();
            token.value = (token.value === 'true');
            expr = node.finishLiteral(token);
        } else if (type === Token.NullLiteral) {
            isAssignmentTarget = isBindingElement = false;
            token = lex();
            token.value = null;
            expr = node.finishLiteral(token);
        } else if (match('/') || match('/=')) {
            isAssignmentTarget = isBindingElement = false;
            index = startIndex;

            if (typeof extra.tokens !== 'undefined') {
                token = collectRegex();
            } else {
                token = scanRegExp();
            }
            lex();
            expr = node.finishLiteral(token);
        } else if (type === Token.Template) {
            expr = parseTemplateLiteral();
        } else {
            throwUnexpectedToken(lex());
        }

        return expr;
    }


    function parseArguments() {
        var args = [], expr;

        expect('(');

        if (!match(')')) {
            while (startIndex < length) {
                if (match('...')) {
                    expr = new Node();
                    lex();
                    expr.finishSpreadElement(isolateCoverGrammar(parseAssignmentExpression));
                } else {
                    expr = isolateCoverGrammar(parseAssignmentExpression);
                }
                args.push(expr);
                if (match(')')) {
                    break;
                }
                expectCommaSeparator();
            }
        }

        expect(')');

        return args;
    }

    function parseNonComputedProperty() {
        var token, node = new Node();

        token = lex();

        if (!isIdentifierName(token)) {
            throwUnexpectedToken(token);
        }

        return node.finishIdentifier(token.value);
    }

    function parseNonComputedMember() {
        expect('.');

        return parseNonComputedProperty();
    }

    function parseComputedMember() {
        var expr;

        expect('[');

        expr = isolateCoverGrammar(parseExpression);

        expect(']');

        return expr;
    }


    function parseNewExpression() {
        var callee, args, node = new Node();

        expectKeyword('new');

        if (match('.')) {
            lex();
            if (lookahead.type === Token.Identifier && lookahead.value === 'target') {
                if (state.inFunctionBody) {
                    lex();
                    return node.finishMetaProperty('new', 'target');
                }
            }
            throwUnexpectedToken(lookahead);
        }

        callee = isolateCoverGrammar(parseLeftHandSideExpression);
        args = match('(') ? parseArguments() : [];

        isAssignmentTarget = isBindingElement = false;

        return node.finishNewExpression(callee, args);
    }


    function parseLeftHandSideExpressionAllowCall() {
        var quasi, expr, args, property, startToken, previousAllowIn = state.allowIn;

        startToken = lookahead;
        state.allowIn = true;

        if (matchKeyword('super') && state.inFunctionBody) {
            expr = new Node();
            lex();
            expr = expr.finishSuper();
            if (!match('(') && !match('.') && !match('[')) {
                throwUnexpectedToken(lookahead);
            }
        } else {
            expr = inheritCoverGrammar(matchKeyword('new') ? parseNewExpression : parsePrimaryExpression);
        }

        for (;;) {
            if (match('.')) {
                isBindingElement = false;
                isAssignmentTarget = true;
                property = parseNonComputedMember();
                expr = new WrappingNode(startToken).finishMemberExpression('.', expr, property);
            } else if (match('(')) {
                isBindingElement = false;
                isAssignmentTarget = false;
                args = parseArguments();
                expr = new WrappingNode(startToken).finishCallExpression(expr, args);
            } else if (match('[')) {
                isBindingElement = false;
                isAssignmentTarget = true;
                property = parseComputedMember();
                expr = new WrappingNode(startToken).finishMemberExpression('[', expr, property);
            } else if (lookahead.type === Token.Template && lookahead.head) {
                quasi = parseTemplateLiteral();
                expr = new WrappingNode(startToken).finishTaggedTemplateExpression(expr, quasi);
            } else {
                break;
            }
        }
        state.allowIn = previousAllowIn;

        return expr;
    }


    function parseLeftHandSideExpression() {
        var quasi, expr, property, startToken;
        assert(state.allowIn, 'callee of new expression always allow in keyword.');

        startToken = lookahead;

        if (matchKeyword('super') && state.inFunctionBody) {
            expr = new Node();
            lex();
            expr = expr.finishSuper();
            if (!match('[') && !match('.')) {
                throwUnexpectedToken(lookahead);
            }
        } else {
            expr = inheritCoverGrammar(matchKeyword('new') ? parseNewExpression : parsePrimaryExpression);
        }

        for (;;) {
            if (match('[')) {
                isBindingElement = false;
                isAssignmentTarget = true;
                property = parseComputedMember();
                expr = new WrappingNode(startToken).finishMemberExpression('[', expr, property);
            } else if (match('.')) {
                isBindingElement = false;
                isAssignmentTarget = true;
                property = parseNonComputedMember();
                expr = new WrappingNode(startToken).finishMemberExpression('.', expr, property);
            } else if (lookahead.type === Token.Template && lookahead.head) {
                quasi = parseTemplateLiteral();
                expr = new WrappingNode(startToken).finishTaggedTemplateExpression(expr, quasi);
            } else {
                break;
            }
        }
        return expr;
    }


    function parsePostfixExpression() {
        var expr, token, startToken = lookahead;

        expr = inheritCoverGrammar(parseLeftHandSideExpressionAllowCall);

        if (!hasLineTerminator && lookahead.type === Token.Punctuator) {
            if (match('++') || match('--')) {
                if (strict && expr.type === Syntax.Identifier && isRestrictedWord(expr.name)) {
                    tolerateError(Messages.StrictLHSPostfix);
                }

                if (!isAssignmentTarget) {
                    tolerateError(Messages.InvalidLHSInAssignment);
                }

                isAssignmentTarget = isBindingElement = false;

                token = lex();
                expr = new WrappingNode(startToken).finishPostfixExpression(token.value, expr);
            }
        }

        return expr;
    }


    function parseUnaryExpression() {
        var token, expr, startToken;

        if (lookahead.type !== Token.Punctuator && lookahead.type !== Token.Keyword) {
            expr = parsePostfixExpression();
        } else if (match('++') || match('--')) {
            startToken = lookahead;
            token = lex();
            expr = inheritCoverGrammar(parseUnaryExpression);
            if (strict && expr.type === Syntax.Identifier && isRestrictedWord(expr.name)) {
                tolerateError(Messages.StrictLHSPrefix);
            }

            if (!isAssignmentTarget) {
                tolerateError(Messages.InvalidLHSInAssignment);
            }
            expr = new WrappingNode(startToken).finishUnaryExpression(token.value, expr);
            isAssignmentTarget = isBindingElement = false;
        } else if (match('+') || match('-') || match('~') || match('!')) {
            startToken = lookahead;
            token = lex();
            expr = inheritCoverGrammar(parseUnaryExpression);
            expr = new WrappingNode(startToken).finishUnaryExpression(token.value, expr);
            isAssignmentTarget = isBindingElement = false;
        } else if (matchKeyword('delete') || matchKeyword('void') || matchKeyword('typeof')) {
            startToken = lookahead;
            token = lex();
            expr = inheritCoverGrammar(parseUnaryExpression);
            expr = new WrappingNode(startToken).finishUnaryExpression(token.value, expr);
            if (strict && expr.operator === 'delete' && expr.argument.type === Syntax.Identifier) {
                tolerateError(Messages.StrictDelete);
            }
            isAssignmentTarget = isBindingElement = false;
        } else {
            expr = parsePostfixExpression();
        }

        return expr;
    }

    function binaryPrecedence(token, allowIn) {
        var prec = 0;

        if (token.type !== Token.Punctuator && token.type !== Token.Keyword) {
            return 0;
        }

        switch (token.value) {
            case '||':
                prec = 1;
                break;

            case '&&':
                prec = 2;
                break;

            case '|':
                prec = 3;
                break;

            case '^':
                prec = 4;
                break;

            case '&':
                prec = 5;
                break;

            case '==':
            case '!=':
            case '===':
            case '!==':
                prec = 6;
                break;

            case '<':
            case '>':
            case '<=':
            case '>=':
            case 'instanceof':
                prec = 7;
                break;

            case 'in':
                prec = allowIn ? 7 : 0;
                break;

            case '<<':
            case '>>':
            case '>>>':
                prec = 8;
                break;

            case '+':
            case '-':
                prec = 9;
                break;

            case '*':
            case '/':
            case '%':
                prec = 11;
                break;

            default:
                break;
        }

        return prec;
    }


    function parseBinaryExpression() {
        var marker, markers, expr, token, prec, stack, right, operator, left, i;

        marker = lookahead;
        left = inheritCoverGrammar(parseUnaryExpression);

        token = lookahead;
        prec = binaryPrecedence(token, state.allowIn);
        if (prec === 0) {
            return left;
        }
        isAssignmentTarget = isBindingElement = false;
        token.prec = prec;
        lex();

        markers = [marker, lookahead];
        right = isolateCoverGrammar(parseUnaryExpression);

        stack = [left, token, right];

        while ((prec = binaryPrecedence(lookahead, state.allowIn)) > 0) {

            while ((stack.length > 2) && (prec <= stack[stack.length - 2].prec)) {
                right = stack.pop();
                operator = stack.pop().value;
                left = stack.pop();
                markers.pop();
                expr = new WrappingNode(markers[markers.length - 1]).finishBinaryExpression(operator, left, right);
                stack.push(expr);
            }

            token = lex();
            token.prec = prec;
            stack.push(token);
            markers.push(lookahead);
            expr = isolateCoverGrammar(parseUnaryExpression);
            stack.push(expr);
        }

        i = stack.length - 1;
        expr = stack[i];
        markers.pop();
        while (i > 1) {
            expr = new WrappingNode(markers.pop()).finishBinaryExpression(stack[i - 1].value, stack[i - 2], expr);
            i -= 2;
        }

        return expr;
    }


    function parseConditionalExpression() {
        var expr, previousAllowIn, consequent, alternate, startToken;

        startToken = lookahead;

        expr = inheritCoverGrammar(parseBinaryExpression);
        if (match('?')) {
            lex();
            previousAllowIn = state.allowIn;
            state.allowIn = true;
            consequent = isolateCoverGrammar(parseAssignmentExpression);
            state.allowIn = previousAllowIn;
            expect(':');
            alternate = isolateCoverGrammar(parseAssignmentExpression);

            expr = new WrappingNode(startToken).finishConditionalExpression(expr, consequent, alternate);
            isAssignmentTarget = isBindingElement = false;
        }

        return expr;
    }


    function parseConciseBody() {
        if (match('{')) {
            return parseFunctionSourceElements();
        }
        return isolateCoverGrammar(parseAssignmentExpression);
    }

    function checkPatternParam(options, param) {
        var i;
        switch (param.type) {
            case Syntax.Identifier:
                validateParam(options, param, param.name);
                break;
            case Syntax.RestElement:
                checkPatternParam(options, param.argument);
                break;
            case Syntax.AssignmentPattern:
                checkPatternParam(options, param.left);
                break;
            case Syntax.ArrayPattern:
                for (i = 0; i < param.elements.length; i++) {
                    if (param.elements[i] !== null) {
                        checkPatternParam(options, param.elements[i]);
                    }
                }
                break;
            case Syntax.YieldExpression:
                break;
            default:
                assert(param.type === Syntax.ObjectPattern, 'Invalid type');
                for (i = 0; i < param.properties.length; i++) {
                    checkPatternParam(options, param.properties[i].value);
                }
                break;
        }
    }
    function reinterpretAsCoverFormalsList(expr) {
        var i, len, param, params, defaults, defaultCount, options, token;

        defaults = [];
        defaultCount = 0;
        params = [expr];

        switch (expr.type) {
            case Syntax.Identifier:
                break;
            case PlaceHolders.ArrowParameterPlaceHolder:
                params = expr.params;
                break;
            default:
                return null;
        }

        options = {
            paramSet: {}
        };

        for (i = 0, len = params.length; i < len; i += 1) {
            param = params[i];
            switch (param.type) {
                case Syntax.AssignmentPattern:
                    params[i] = param.left;
                    if (param.right.type === Syntax.YieldExpression) {
                        if (param.right.argument) {
                            throwUnexpectedToken(lookahead);
                        }
                        param.right.type = Syntax.Identifier;
                        param.right.name = 'yield';
                        delete param.right.argument;
                        delete param.right.delegate;
                    }
                    defaults.push(param.right);
                    ++defaultCount;
                    checkPatternParam(options, param.left);
                    break;
                default:
                    checkPatternParam(options, param);
                    params[i] = param;
                    defaults.push(null);
                    break;
            }
        }

        if (strict || !state.allowYield) {
            for (i = 0, len = params.length; i < len; i += 1) {
                param = params[i];
                if (param.type === Syntax.YieldExpression) {
                    throwUnexpectedToken(lookahead);
                }
            }
        }

        if (options.message === Messages.StrictParamDupe) {
            token = strict ? options.stricted : options.firstRestricted;
            throwUnexpectedToken(token, options.message);
        }

        if (defaultCount === 0) {
            defaults = [];
        }

        return {
            params: params,
            defaults: defaults,
            stricted: options.stricted,
            firstRestricted: options.firstRestricted,
            message: options.message
        };
    }

    function parseArrowFunctionExpression(options, node) {
        var previousStrict, previousAllowYield, body;

        if (hasLineTerminator) {
            tolerateUnexpectedToken(lookahead);
        }
        expect('=>');

        previousStrict = strict;
        previousAllowYield = state.allowYield;
        state.allowYield = true;

        body = parseConciseBody();

        if (strict && options.firstRestricted) {
            throwUnexpectedToken(options.firstRestricted, options.message);
        }
        if (strict && options.stricted) {
            tolerateUnexpectedToken(options.stricted, options.message);
        }

        strict = previousStrict;
        state.allowYield = previousAllowYield;

        return node.finishArrowFunctionExpression(options.params, options.defaults, body, body.type !== Syntax.BlockStatement);
    }


    function parseYieldExpression() {
        var argument, expr, delegate, previousAllowYield;

        argument = null;
        expr = new Node();

        expectKeyword('yield');

        if (!hasLineTerminator) {
            previousAllowYield = state.allowYield;
            state.allowYield = false;
            delegate = match('*');
            if (delegate) {
                lex();
                argument = parseAssignmentExpression();
            } else {
                if (!match(';') && !match('}') && !match(')') && lookahead.type !== Token.EOF) {
                    argument = parseAssignmentExpression();
                }
            }
            state.allowYield = previousAllowYield;
        }

        return expr.finishYieldExpression(argument, delegate);
    }


    function parseAssignmentExpression() {
        var token, expr, right, list, startToken;

        startToken = lookahead;
        token = lookahead;

        if (!state.allowYield && matchKeyword('yield')) {
            return parseYieldExpression();
        }

        expr = parseConditionalExpression();

        if (expr.type === PlaceHolders.ArrowParameterPlaceHolder || match('=>')) {
            isAssignmentTarget = isBindingElement = false;
            list = reinterpretAsCoverFormalsList(expr);

            if (list) {
                firstCoverInitializedNameError = null;
                return parseArrowFunctionExpression(list, new WrappingNode(startToken));
            }

            return expr;
        }

        if (matchAssign()) {
            if (!isAssignmentTarget) {
                tolerateError(Messages.InvalidLHSInAssignment);
            }

            if (strict && expr.type === Syntax.Identifier) {
                if (isRestrictedWord(expr.name)) {
                    tolerateUnexpectedToken(token, Messages.StrictLHSAssignment);
                }
                if (isStrictModeReservedWord(expr.name)) {
                    tolerateUnexpectedToken(token, Messages.StrictReservedWord);
                }
            }

            if (!match('=')) {
                isAssignmentTarget = isBindingElement = false;
            } else {
                reinterpretExpressionAsPattern(expr);
            }

            token = lex();
            right = isolateCoverGrammar(parseAssignmentExpression);
            expr = new WrappingNode(startToken).finishAssignmentExpression(token.value, expr, right);
            firstCoverInitializedNameError = null;
        }

        return expr;
    }


    function parseExpression() {
        var expr, startToken = lookahead, expressions;

        expr = isolateCoverGrammar(parseAssignmentExpression);

        if (match(',')) {
            expressions = [expr];

            while (startIndex < length) {
                if (!match(',')) {
                    break;
                }
                lex();
                expressions.push(isolateCoverGrammar(parseAssignmentExpression));
            }

            expr = new WrappingNode(startToken).finishSequenceExpression(expressions);
        }

        return expr;
    }


    function parseStatementListItem() {
        if (lookahead.type === Token.Keyword) {
            switch (lookahead.value) {
                case 'export':
                    if (state.sourceType !== 'module') {
                        tolerateUnexpectedToken(lookahead, Messages.IllegalExportDeclaration);
                    }
                    return parseExportDeclaration();
                case 'import':
                    if (state.sourceType !== 'module') {
                        tolerateUnexpectedToken(lookahead, Messages.IllegalImportDeclaration);
                    }
                    return parseImportDeclaration();
                case 'const':
                    return parseLexicalDeclaration({inFor: false});
                case 'function':
                    return parseFunctionDeclaration(new Node());
                case 'class':
                    return parseClassDeclaration();
            }
        }

        if (matchKeyword('let') && isLexicalDeclaration()) {
            return parseLexicalDeclaration({inFor: false});
        }

        return parseStatement();
    }

    function parseStatementList() {
        var list = [];
        while (startIndex < length) {
            if (match('}')) {
                break;
            }
            list.push(parseStatementListItem());
        }

        return list;
    }

    function parseBlock() {
        var block, node = new Node();

        expect('{');

        block = parseStatementList();

        expect('}');

        return node.finishBlockStatement(block);
    }


    function parseVariableIdentifier(kind) {
        var token, node = new Node();

        token = lex();

        if (token.type === Token.Keyword && token.value === 'yield') {
            if (strict) {
                tolerateUnexpectedToken(token, Messages.StrictReservedWord);
            } if (!state.allowYield) {
                throwUnexpectedToken(token);
            }
        } else if (token.type !== Token.Identifier) {
            if (strict && token.type === Token.Keyword && isStrictModeReservedWord(token.value)) {
                tolerateUnexpectedToken(token, Messages.StrictReservedWord);
            } else {
                if (strict || token.value !== 'let' || kind !== 'var') {
                    throwUnexpectedToken(token);
                }
            }
        } else if (state.sourceType === 'module' && token.type === Token.Identifier && token.value === 'await') {
            tolerateUnexpectedToken(token);
        }

        return node.finishIdentifier(token.value);
    }

    function parseVariableDeclaration(options) {
        var init = null, id, node = new Node(), params = [];

        id = parsePattern(params, 'var');

        if (strict && isRestrictedWord(id.name)) {
            tolerateError(Messages.StrictVarName);
        }

        if (match('=')) {
            lex();
            init = isolateCoverGrammar(parseAssignmentExpression);
        } else if (id.type !== Syntax.Identifier && !options.inFor) {
            expect('=');
        }

        return node.finishVariableDeclarator(id, init);
    }

    function parseVariableDeclarationList(options) {
        var list = [];

        do {
            list.push(parseVariableDeclaration({ inFor: options.inFor }));
            if (!match(',')) {
                break;
            }
            lex();
        } while (startIndex < length);

        return list;
    }

    function parseVariableStatement(node) {
        var declarations;

        expectKeyword('var');

        declarations = parseVariableDeclarationList({ inFor: false });

        consumeSemicolon();

        return node.finishVariableDeclaration(declarations);
    }


    function parseLexicalBinding(kind, options) {
        var init = null, id, node = new Node(), params = [];

        id = parsePattern(params, kind);

        if (strict && id.type === Syntax.Identifier && isRestrictedWord(id.name)) {
            tolerateError(Messages.StrictVarName);
        }

        if (kind === 'const') {
            if (!matchKeyword('in') && !matchContextualKeyword('of')) {
                expect('=');
                init = isolateCoverGrammar(parseAssignmentExpression);
            }
        } else if ((!options.inFor && id.type !== Syntax.Identifier) || match('=')) {
            expect('=');
            init = isolateCoverGrammar(parseAssignmentExpression);
        }

        return node.finishVariableDeclarator(id, init);
    }

    function parseBindingList(kind, options) {
        var list = [];

        do {
            list.push(parseLexicalBinding(kind, options));
            if (!match(',')) {
                break;
            }
            lex();
        } while (startIndex < length);

        return list;
    }


    function tokenizerState() {
        return {
            index: index,
            lineNumber: lineNumber,
            lineStart: lineStart,
            hasLineTerminator: hasLineTerminator,
            lastIndex: lastIndex,
            lastLineNumber: lastLineNumber,
            lastLineStart: lastLineStart,
            startIndex: startIndex,
            startLineNumber: startLineNumber,
            startLineStart: startLineStart,
            lookahead: lookahead,
            tokenCount: extra.tokens ? extra.tokens.length : 0
        };
    }

    function resetTokenizerState(ts) {
        index = ts.index;
        lineNumber = ts.lineNumber;
        lineStart = ts.lineStart;
        hasLineTerminator = ts.hasLineTerminator;
        lastIndex = ts.lastIndex;
        lastLineNumber = ts.lastLineNumber;
        lastLineStart = ts.lastLineStart;
        startIndex = ts.startIndex;
        startLineNumber = ts.startLineNumber;
        startLineStart = ts.startLineStart;
        lookahead = ts.lookahead;
        if (extra.tokens) {
            extra.tokens.splice(ts.tokenCount, extra.tokens.length);
        }
    }

    function isLexicalDeclaration() {
        var lexical, ts;

        ts = tokenizerState();

        lex();
        lexical = (lookahead.type === Token.Identifier) || match('[') || match('{') ||
        matchKeyword('let') || matchKeyword('yield');

        resetTokenizerState(ts);

        return lexical;
    }

    function parseLexicalDeclaration(options) {
        var kind, declarations, node = new Node();

        kind = lex().value;
        assert(kind === 'let' || kind === 'const', 'Lexical declaration must be either let or const');

        declarations = parseBindingList(kind, options);

        consumeSemicolon();

        return node.finishLexicalDeclaration(declarations, kind);
    }

    function parseRestElement(params) {
        var param, node = new Node();

        lex();

        if (match('{')) {
            throwError(Messages.ObjectPatternAsRestParameter);
        }

        params.push(lookahead);

        param = parseVariableIdentifier();

        if (match('=')) {
            throwError(Messages.DefaultRestParameter);
        }

        if (!match(')')) {
            throwError(Messages.ParameterAfterRestParameter);
        }

        return node.finishRestElement(param);
    }


    function parseEmptyStatement(node) {
        expect(';');
        return node.finishEmptyStatement();
    }


    function parseExpressionStatement(node) {
        var expr = parseExpression();
        consumeSemicolon();
        return node.finishExpressionStatement(expr);
    }


    function parseIfStatement(node) {
        var test, consequent, alternate;

        expectKeyword('if');

        expect('(');

        test = parseExpression();

        expect(')');

        consequent = parseStatement();

        if (matchKeyword('else')) {
            lex();
            alternate = parseStatement();
        } else {
            alternate = null;
        }

        return node.finishIfStatement(test, consequent, alternate);
    }


    function parseDoWhileStatement(node) {
        var body, test, oldInIteration;

        expectKeyword('do');

        oldInIteration = state.inIteration;
        state.inIteration = true;

        body = parseStatement();

        state.inIteration = oldInIteration;

        expectKeyword('while');

        expect('(');

        test = parseExpression();

        expect(')');

        if (match(';')) {
            lex();
        }

        return node.finishDoWhileStatement(body, test);
    }

    function parseWhileStatement(node) {
        var test, body, oldInIteration;

        expectKeyword('while');

        expect('(');

        test = parseExpression();

        expect(')');

        oldInIteration = state.inIteration;
        state.inIteration = true;

        body = parseStatement();

        state.inIteration = oldInIteration;

        return node.finishWhileStatement(test, body);
    }

    function parseForStatement(node) {
        var init, forIn, initSeq, initStartToken, test, update, left, right, kind, declarations,
            body, oldInIteration, previousAllowIn = state.allowIn;

        init = test = update = null;
        forIn = true;

        expectKeyword('for');

        expect('(');

        if (match(';')) {
            lex();
        } else {
            if (matchKeyword('var')) {
                init = new Node();
                lex();

                state.allowIn = false;
                declarations = parseVariableDeclarationList({ inFor: true });
                state.allowIn = previousAllowIn;

                if (declarations.length === 1 && matchKeyword('in')) {
                    init = init.finishVariableDeclaration(declarations);
                    lex();
                    left = init;
                    right = parseExpression();
                    init = null;
                } else if (declarations.length === 1 && declarations[0].init === null && matchContextualKeyword('of')) {
                    init = init.finishVariableDeclaration(declarations);
                    lex();
                    left = init;
                    right = parseAssignmentExpression();
                    init = null;
                    forIn = false;
                } else {
                    init = init.finishVariableDeclaration(declarations);
                    expect(';');
                }
            } else if (matchKeyword('const') || matchKeyword('let')) {
                init = new Node();
                kind = lex().value;

                state.allowIn = false;
                declarations = parseBindingList(kind, {inFor: true});
                state.allowIn = previousAllowIn;

                if (declarations.length === 1 && declarations[0].init === null && matchKeyword('in')) {
                    init = init.finishLexicalDeclaration(declarations, kind);
                    lex();
                    left = init;
                    right = parseExpression();
                    init = null;
                } else if (declarations.length === 1 && declarations[0].init === null && matchContextualKeyword('of')) {
                    init = init.finishLexicalDeclaration(declarations, kind);
                    lex();
                    left = init;
                    right = parseAssignmentExpression();
                    init = null;
                    forIn = false;
                } else {
                    consumeSemicolon();
                    init = init.finishLexicalDeclaration(declarations, kind);
                }
            } else {
                initStartToken = lookahead;
                state.allowIn = false;
                init = inheritCoverGrammar(parseAssignmentExpression);
                state.allowIn = previousAllowIn;

                if (matchKeyword('in')) {
                    if (!isAssignmentTarget) {
                        tolerateError(Messages.InvalidLHSInForIn);
                    }

                    lex();
                    reinterpretExpressionAsPattern(init);
                    left = init;
                    right = parseExpression();
                    init = null;
                } else if (matchContextualKeyword('of')) {
                    if (!isAssignmentTarget) {
                        tolerateError(Messages.InvalidLHSInForLoop);
                    }

                    lex();
                    reinterpretExpressionAsPattern(init);
                    left = init;
                    right = parseAssignmentExpression();
                    init = null;
                    forIn = false;
                } else {
                    if (match(',')) {
                        initSeq = [init];
                        while (match(',')) {
                            lex();
                            initSeq.push(isolateCoverGrammar(parseAssignmentExpression));
                        }
                        init = new WrappingNode(initStartToken).finishSequenceExpression(initSeq);
                    }
                    expect(';');
                }
            }
        }

        if (typeof left === 'undefined') {

            if (!match(';')) {
                test = parseExpression();
            }
            expect(';');

            if (!match(')')) {
                update = parseExpression();
            }
        }

        expect(')');

        oldInIteration = state.inIteration;
        state.inIteration = true;

        body = isolateCoverGrammar(parseStatement);

        state.inIteration = oldInIteration;
        
        bm_eventDispatcher.log('------');
        bm_eventDispatcher.log(typeof left);
        bm_eventDispatcher.log(left);
        if(typeof left === 'undefined'){
            return node.finishForStatement(init, test, update, body);
        } else if(forIn){
            return node.finishForInStatement(left, right, body);
        } else {
            return node.finishForOfStatement(left, right, body);
        }
    }


    function parseContinueStatement(node) {
        var label = null, key;

        expectKeyword('continue');

        if (source.charCodeAt(startIndex) === 0x3B) {
            lex();

            if (!state.inIteration) {
                throwError(Messages.IllegalContinue);
            }

            return node.finishContinueStatement(null);
        }

        if (hasLineTerminator) {
            if (!state.inIteration) {
                throwError(Messages.IllegalContinue);
            }

            return node.finishContinueStatement(null);
        }

        if (lookahead.type === Token.Identifier) {
            label = parseVariableIdentifier();

            key = '$' + label.name;
            if (!Object.prototype.hasOwnProperty.call(state.labelSet, key)) {
                throwError(Messages.UnknownLabel, label.name);
            }
        }

        consumeSemicolon();

        if (label === null && !state.inIteration) {
            throwError(Messages.IllegalContinue);
        }

        return node.finishContinueStatement(label);
    }


    function parseBreakStatement(node) {
        var label = null, key;

        expectKeyword('break');

        if (source.charCodeAt(lastIndex) === 0x3B) {
            lex();

            if (!(state.inIteration || state.inSwitch)) {
                throwError(Messages.IllegalBreak);
            }

            return node.finishBreakStatement(null);
        }

        if (hasLineTerminator) {
            if (!(state.inIteration || state.inSwitch)) {
                throwError(Messages.IllegalBreak);
            }
        } else if (lookahead.type === Token.Identifier) {
            label = parseVariableIdentifier();

            key = '$' + label.name;
            if (!Object.prototype.hasOwnProperty.call(state.labelSet, key)) {
                throwError(Messages.UnknownLabel, label.name);
            }
        }

        consumeSemicolon();

        if (label === null && !(state.inIteration || state.inSwitch)) {
            throwError(Messages.IllegalBreak);
        }

        return node.finishBreakStatement(label);
    }


    function parseReturnStatement(node) {
        var argument = null;

        expectKeyword('return');

        if (!state.inFunctionBody) {
            tolerateError(Messages.IllegalReturn);
        }

        if (source.charCodeAt(lastIndex) === 0x20) {
            if (isIdentifierStart(source.charCodeAt(lastIndex + 1))) {
                argument = parseExpression();
                consumeSemicolon();
                return node.finishReturnStatement(argument);
            }
        }

        if (hasLineTerminator) {
            return node.finishReturnStatement(null);
        }

        if (!match(';')) {
            if (!match('}') && lookahead.type !== Token.EOF) {
                argument = parseExpression();
            }
        }

        consumeSemicolon();

        return node.finishReturnStatement(argument);
    }


    function parseWithStatement(node) {
        var object, body;

        if (strict) {
            tolerateError(Messages.StrictModeWith);
        }

        expectKeyword('with');

        expect('(');

        object = parseExpression();

        expect(')');

        body = parseStatement();

        return node.finishWithStatement(object, body);
    }


    function parseSwitchCase() {
        var test, consequent = [], statement, node = new Node();

        if (matchKeyword('default')) {
            lex();
            test = null;
        } else {
            expectKeyword('case');
            test = parseExpression();
        }
        expect(':');

        while (startIndex < length) {
            if (match('}') || matchKeyword('default') || matchKeyword('case')) {
                break;
            }
            statement = parseStatementListItem();
            consequent.push(statement);
        }

        return node.finishSwitchCase(test, consequent);
    }

    function parseSwitchStatement(node) {
        var discriminant, cases, clause, oldInSwitch, defaultFound;

        expectKeyword('switch');

        expect('(');

        discriminant = parseExpression();

        expect(')');

        expect('{');

        cases = [];

        if (match('}')) {
            lex();
            return node.finishSwitchStatement(discriminant, cases);
        }

        oldInSwitch = state.inSwitch;
        state.inSwitch = true;
        defaultFound = false;

        while (startIndex < length) {
            if (match('}')) {
                break;
            }
            clause = parseSwitchCase();
            if (clause.test === null) {
                if (defaultFound) {
                    throwError(Messages.MultipleDefaultsInSwitch);
                }
                defaultFound = true;
            }
            cases.push(clause);
        }

        state.inSwitch = oldInSwitch;

        expect('}');

        return node.finishSwitchStatement(discriminant, cases);
    }


    function parseThrowStatement(node) {
        var argument;

        expectKeyword('throw');

        if (hasLineTerminator) {
            throwError(Messages.NewlineAfterThrow);
        }

        argument = parseExpression();

        consumeSemicolon();

        return node.finishThrowStatement(argument);
    }


    function parseCatchClause() {
        var param, params = [], paramMap = {}, key, i, body, node = new Node();

        expectKeyword('catch');

        expect('(');
        if (match(')')) {
            throwUnexpectedToken(lookahead);
        }

        param = parsePattern(params);
        for (i = 0; i < params.length; i++) {
            key = '$' + params[i].value;
            if (Object.prototype.hasOwnProperty.call(paramMap, key)) {
                tolerateError(Messages.DuplicateBinding, params[i].value);
            }
            paramMap[key] = true;
        }

        if (strict && isRestrictedWord(param.name)) {
            tolerateError(Messages.StrictCatchVariable);
        }

        expect(')');
        body = parseBlock();
        return node.finishCatchClause(param, body);
    }

    function parseTryStatement(node) {
        var block, handler = null, finalizer = null;

        expectKeyword('try');

        block = parseBlock();

        if (matchKeyword('catch')) {
            handler = parseCatchClause();
        }

        if (matchKeyword('finally')) {
            lex();
            finalizer = parseBlock();
        }

        if (!handler && !finalizer) {
            throwError(Messages.NoCatchOrFinally);
        }

        return node.finishTryStatement(block, handler, finalizer);
    }


    function parseDebuggerStatement(node) {
        expectKeyword('debugger');

        consumeSemicolon();

        return node.finishDebuggerStatement();
    }


    function parseStatement() {
        var type = lookahead.type,
            expr,
            labeledBody,
            key,
            node;

        if (type === Token.EOF) {
            throwUnexpectedToken(lookahead);
        }

        if (type === Token.Punctuator && lookahead.value === '{') {
            return parseBlock();
        }
        isAssignmentTarget = isBindingElement = true;
        node = new Node();

        if (type === Token.Punctuator) {
            switch (lookahead.value) {
                case ';':
                    return parseEmptyStatement(node);
                case '(':
                    return parseExpressionStatement(node);
                default:
                    break;
            }
        } else if (type === Token.Keyword) {
            switch (lookahead.value) {
                case 'break':
                    return parseBreakStatement(node);
                case 'continue':
                    return parseContinueStatement(node);
                case 'debugger':
                    return parseDebuggerStatement(node);
                case 'do':
                    return parseDoWhileStatement(node);
                case 'for':
                    return parseForStatement(node);
                case 'function':
                    return parseFunctionDeclaration(node);
                case 'if':
                    return parseIfStatement(node);
                case 'return':
                    return parseReturnStatement(node);
                case 'switch':
                    return parseSwitchStatement(node);
                case 'throw':
                    return parseThrowStatement(node);
                case 'try':
                    return parseTryStatement(node);
                case 'var':
                    return parseVariableStatement(node);
                case 'while':
                    return parseWhileStatement(node);
                case 'with':
                    return parseWithStatement(node);
                default:
                    break;
            }
        }

        expr = parseExpression();

        if ((expr.type === Syntax.Identifier) && match(':')) {
            lex();

            key = '$' + expr.name;
            if (Object.prototype.hasOwnProperty.call(state.labelSet, key)) {
                throwError(Messages.Redeclaration, 'Label', expr.name);
            }

            state.labelSet[key] = true;
            labeledBody = parseStatement();
            delete state.labelSet[key];
            return node.finishLabeledStatement(expr, labeledBody);
        }

        consumeSemicolon();

        return node.finishExpressionStatement(expr);
    }


    function parseFunctionSourceElements() {
        var statement, body = [], token, directive, firstRestricted,
            oldLabelSet, oldInIteration, oldInSwitch, oldInFunctionBody, oldParenthesisCount,
            node = new Node();

        expect('{');

        while (startIndex < length) {
            if (lookahead.type !== Token.StringLiteral) {
                break;
            }
            token = lookahead;

            statement = parseStatementListItem();
            body.push(statement);
            if (statement.expression.type !== Syntax.Literal) {
                break;
            }
            directive = source.slice(token.start + 1, token.end - 1);
            if (directive === 'use strict') {
                strict = true;
                if (firstRestricted) {
                    tolerateUnexpectedToken(firstRestricted, Messages.StrictOctalLiteral);
                }
            } else {
                if (!firstRestricted && token.octal) {
                    firstRestricted = token;
                }
            }
        }

        oldLabelSet = state.labelSet;
        oldInIteration = state.inIteration;
        oldInSwitch = state.inSwitch;
        oldInFunctionBody = state.inFunctionBody;
        oldParenthesisCount = state.parenthesizedCount;

        state.labelSet = {};
        state.inIteration = false;
        state.inSwitch = false;
        state.inFunctionBody = true;
        state.parenthesizedCount = 0;

        while (startIndex < length) {
            if (match('}')) {
                break;
            }
            body.push(parseStatementListItem());
        }

        expect('}');

        state.labelSet = oldLabelSet;
        state.inIteration = oldInIteration;
        state.inSwitch = oldInSwitch;
        state.inFunctionBody = oldInFunctionBody;
        state.parenthesizedCount = oldParenthesisCount;

        return node.finishBlockStatement(body);
    }

    function validateParam(options, param, name) {
        var key = '$' + name;
        if (strict) {
            if (isRestrictedWord(name)) {
                options.stricted = param;
                options.message = Messages.StrictParamName;
            }
            if (Object.prototype.hasOwnProperty.call(options.paramSet, key)) {
                options.stricted = param;
                options.message = Messages.StrictParamDupe;
            }
        } else if (!options.firstRestricted) {
            if (isRestrictedWord(name)) {
                options.firstRestricted = param;
                options.message = Messages.StrictParamName;
            } else if (isStrictModeReservedWord(name)) {
                options.firstRestricted = param;
                options.message = Messages.StrictReservedWord;
            } else if (Object.prototype.hasOwnProperty.call(options.paramSet, key)) {
                options.stricted = param;
                options.message = Messages.StrictParamDupe;
            }
        }
        options.paramSet[key] = true;
    }

    function parseParam(options) {
        var token, param, params = [], i, def;

        token = lookahead;
        if (token.value === '...') {
            param = parseRestElement(params);
            validateParam(options, param.argument, param.argument.name);
            options.params.push(param);
            options.defaults.push(null);
            return false;
        }

        param = parsePatternWithDefault(params);
        for (i = 0; i < params.length; i++) {
            validateParam(options, params[i], params[i].value);
        }

        if (param.type === Syntax.AssignmentPattern) {
            def = param.right;
            param = param.left;
            ++options.defaultCount;
        }

        options.params.push(param);
        options.defaults.push(def);

        return !match(')');
    }

    function parseParams(firstRestricted) {
        var options;

        options = {
            params: [],
            defaultCount: 0,
            defaults: [],
            firstRestricted: firstRestricted
        };

        expect('(');

        if (!match(')')) {
            options.paramSet = {};
            while (startIndex < length) {
                if (!parseParam(options)) {
                    break;
                }
                expect(',');
            }
        }

        expect(')');

        if (options.defaultCount === 0) {
            options.defaults = [];
        }

        return {
            params: options.params,
            defaults: options.defaults,
            stricted: options.stricted,
            firstRestricted: options.firstRestricted,
            message: options.message
        };
    }

    function parseFunctionDeclaration(node, identifierIsOptional) {
        var id = null, params = [], defaults = [], body, token, stricted, tmp, firstRestricted, message, previousStrict,
            isGenerator, previousAllowYield;

        previousAllowYield = state.allowYield;

        expectKeyword('function');

        isGenerator = match('*');
        if (isGenerator) {
            lex();
        }

        if (!identifierIsOptional || !match('(')) {
            token = lookahead;
            id = parseVariableIdentifier();
            if (strict) {
                if (isRestrictedWord(token.value)) {
                    tolerateUnexpectedToken(token, Messages.StrictFunctionName);
                }
            } else {
                if (isRestrictedWord(token.value)) {
                    firstRestricted = token;
                    message = Messages.StrictFunctionName;
                } else if (isStrictModeReservedWord(token.value)) {
                    firstRestricted = token;
                    message = Messages.StrictReservedWord;
                }
            }
        }

        state.allowYield = !isGenerator;
        tmp = parseParams(firstRestricted);
        params = tmp.params;
        defaults = tmp.defaults;
        stricted = tmp.stricted;
        firstRestricted = tmp.firstRestricted;
        if (tmp.message) {
            message = tmp.message;
        }


        previousStrict = strict;
        body = parseFunctionSourceElements();
        if (strict && firstRestricted) {
            throwUnexpectedToken(firstRestricted, message);
        }
        if (strict && stricted) {
            tolerateUnexpectedToken(stricted, message);
        }

        strict = previousStrict;
        state.allowYield = previousAllowYield;

        return node.finishFunctionDeclaration(id, params, defaults, body, isGenerator);
    }

    function parseFunctionExpression() {
        var token, id = null, stricted, firstRestricted, message, tmp,
            params = [], defaults = [], body, previousStrict, node = new Node(),
            isGenerator, previousAllowYield;

        previousAllowYield = state.allowYield;

        expectKeyword('function');

        isGenerator = match('*');
        if (isGenerator) {
            lex();
        }

        state.allowYield = !isGenerator;
        if (!match('(')) {
            token = lookahead;
            id = (!strict && !isGenerator && matchKeyword('yield')) ? parseNonComputedProperty() : parseVariableIdentifier();
            if (strict) {
                if (isRestrictedWord(token.value)) {
                    tolerateUnexpectedToken(token, Messages.StrictFunctionName);
                }
            } else {
                if (isRestrictedWord(token.value)) {
                    firstRestricted = token;
                    message = Messages.StrictFunctionName;
                } else if (isStrictModeReservedWord(token.value)) {
                    firstRestricted = token;
                    message = Messages.StrictReservedWord;
                }
            }
        }

        tmp = parseParams(firstRestricted);
        params = tmp.params;
        defaults = tmp.defaults;
        stricted = tmp.stricted;
        firstRestricted = tmp.firstRestricted;
        if (tmp.message) {
            message = tmp.message;
        }

        previousStrict = strict;
        body = parseFunctionSourceElements();
        if (strict && firstRestricted) {
            throwUnexpectedToken(firstRestricted, message);
        }
        if (strict && stricted) {
            tolerateUnexpectedToken(stricted, message);
        }
        strict = previousStrict;
        state.allowYield = previousAllowYield;

        return node.finishFunctionExpression(id, params, defaults, body, isGenerator);
    }


    function parseClassBody() {
        var classBody, token, isStatic, hasConstructor = false, body, method, computed, key;

        classBody = new Node();

        expect('{');
        body = [];
        while (!match('}')) {
            if (match(';')) {
                lex();
            } else {
                method = new Node();
                token = lookahead;
                isStatic = false;
                computed = match('[');
                if (match('*')) {
                    lex();
                } else {
                    key = parseObjectPropertyKey();
                    if (key.name === 'static' && (lookaheadPropertyName() || match('*'))) {
                        token = lookahead;
                        isStatic = true;
                        computed = match('[');
                        if (match('*')) {
                            lex();
                        } else {
                            key = parseObjectPropertyKey();
                        }
                    }
                }
                method = tryParseMethodDefinition(token, key, computed, method);
                if (method) {
                    method['static'] = isStatic;
                    if (method.kind === 'init') {
                        method.kind = 'method';
                    }
                    if (!isStatic) {
                        if (!method.computed && (method.key.name || method.key.value.toString()) === 'constructor') {
                            if (method.kind !== 'method' || !method.method || method.value.generator) {
                                throwUnexpectedToken(token, Messages.ConstructorSpecialMethod);
                            }
                            if (hasConstructor) {
                                throwUnexpectedToken(token, Messages.DuplicateConstructor);
                            } else {
                                hasConstructor = true;
                            }
                            method.kind = 'constructor';
                        }
                    } else {
                        if (!method.computed && (method.key.name || method.key.value.toString()) === 'prototype') {
                            throwUnexpectedToken(token, Messages.StaticPrototype);
                        }
                    }
                    method.type = Syntax.MethodDefinition;
                    delete method.method;
                    delete method.shorthand;
                    body.push(method);
                } else {
                    throwUnexpectedToken(lookahead);
                }
            }
        }
        lex();
        return classBody.finishClassBody(body);
    }

    function parseClassDeclaration(identifierIsOptional) {
        var id = null, superClass = null, classNode = new Node(), classBody, previousStrict = strict;
        strict = true;

        expectKeyword('class');

        if (!identifierIsOptional || lookahead.type === Token.Identifier) {
            id = parseVariableIdentifier();
        }

        if (matchKeyword('extends')) {
            lex();
            superClass = isolateCoverGrammar(parseLeftHandSideExpressionAllowCall);
        }
        classBody = parseClassBody();
        strict = previousStrict;

        return classNode.finishClassDeclaration(id, superClass, classBody);
    }

    function parseClassExpression() {
        var id = null, superClass = null, classNode = new Node(), classBody, previousStrict = strict;
        strict = true;

        expectKeyword('class');

        if (lookahead.type === Token.Identifier) {
            id = parseVariableIdentifier();
        }

        if (matchKeyword('extends')) {
            lex();
            superClass = isolateCoverGrammar(parseLeftHandSideExpressionAllowCall);
        }
        classBody = parseClassBody();
        strict = previousStrict;

        return classNode.finishClassExpression(id, superClass, classBody);
    }


    function parseModuleSpecifier() {
        var node = new Node();

        if (lookahead.type !== Token.StringLiteral) {
            throwError(Messages.InvalidModuleSpecifier);
        }
        return node.finishLiteral(lex());
    }


    function parseExportSpecifier() {
        var exported, local, node = new Node(), def;
        if (matchKeyword('default')) {
            def = new Node();
            lex();
            local = def.finishIdentifier('default');
        } else {
            local = parseVariableIdentifier();
        }
        if (matchContextualKeyword('as')) {
            lex();
            exported = parseNonComputedProperty();
        }
        return node.finishExportSpecifier(local, exported);
    }

    function parseExportNamedDeclaration(node) {
        var declaration = null,
            isExportFromIdentifier,
            src = null, specifiers = [];

        if (lookahead.type === Token.Keyword) {
            switch (lookahead.value) {
                case 'let':
                case 'const':
                    declaration = parseLexicalDeclaration({inFor: false});
                    return node.finishExportNamedDeclaration(declaration, specifiers, null);
                case 'var':
                case 'class':
                case 'function':
                    declaration = parseStatementListItem();
                    return node.finishExportNamedDeclaration(declaration, specifiers, null);
            }
        }

        expect('{');
        while (!match('}')) {
            isExportFromIdentifier = isExportFromIdentifier || matchKeyword('default');
            specifiers.push(parseExportSpecifier());
            if (!match('}')) {
                expect(',');
                if (match('}')) {
                    break;
                }
            }
        }
        expect('}');

        if (matchContextualKeyword('from')) {
            lex();
            src = parseModuleSpecifier();
            consumeSemicolon();
        } else if (isExportFromIdentifier) {
            throwError(lookahead.value ?
                Messages.UnexpectedToken : Messages.MissingFromClause, lookahead.value);
        } else {
            consumeSemicolon();
        }
        return node.finishExportNamedDeclaration(declaration, specifiers, src);
    }

    function parseExportDefaultDeclaration(node) {
        var declaration = null,
            expression = null;

        expectKeyword('default');

        if (matchKeyword('function')) {
            declaration = parseFunctionDeclaration(new Node(), true);
            return node.finishExportDefaultDeclaration(declaration);
        }
        if (matchKeyword('class')) {
            declaration = parseClassDeclaration(true);
            return node.finishExportDefaultDeclaration(declaration);
        }

        if (matchContextualKeyword('from')) {
            throwError(Messages.UnexpectedToken, lookahead.value);
        }

        if (match('{')) {
            expression = parseObjectInitializer();
        } else if (match('[')) {
            expression = parseArrayInitializer();
        } else {
            expression = parseAssignmentExpression();
        }
        consumeSemicolon();
        return node.finishExportDefaultDeclaration(expression);
    }

    function parseExportAllDeclaration(node) {
        var src;

        expect('*');
        if (!matchContextualKeyword('from')) {
            throwError(lookahead.value ?
                Messages.UnexpectedToken : Messages.MissingFromClause, lookahead.value);
        }
        lex();
        src = parseModuleSpecifier();
        consumeSemicolon();

        return node.finishExportAllDeclaration(src);
    }

    function parseExportDeclaration() {
        var node = new Node();
        if (state.inFunctionBody) {
            throwError(Messages.IllegalExportDeclaration);
        }

        expectKeyword('export');

        if (matchKeyword('default')) {
            return parseExportDefaultDeclaration(node);
        }
        if (match('*')) {
            return parseExportAllDeclaration(node);
        }
        return parseExportNamedDeclaration(node);
    }


    function parseImportSpecifier() {
        var local, imported, node = new Node();

        imported = parseNonComputedProperty();
        if (matchContextualKeyword('as')) {
            lex();
            local = parseVariableIdentifier();
        }

        return node.finishImportSpecifier(local, imported);
    }

    function parseNamedImports() {
        var specifiers = [];
        expect('{');
        while (!match('}')) {
            specifiers.push(parseImportSpecifier());
            if (!match('}')) {
                expect(',');
                if (match('}')) {
                    break;
                }
            }
        }
        expect('}');
        return specifiers;
    }

    function parseImportDefaultSpecifier() {
        var local, node = new Node();

        local = parseNonComputedProperty();

        return node.finishImportDefaultSpecifier(local);
    }

    function parseImportNamespaceSpecifier() {
        var local, node = new Node();

        expect('*');
        if (!matchContextualKeyword('as')) {
            throwError(Messages.NoAsAfterImportNamespace);
        }
        lex();
        local = parseNonComputedProperty();

        return node.finishImportNamespaceSpecifier(local);
    }

    function parseImportDeclaration() {
        var specifiers = [], src, node = new Node();

        if (state.inFunctionBody) {
            throwError(Messages.IllegalImportDeclaration);
        }

        expectKeyword('import');

        if (lookahead.type === Token.StringLiteral) {
            src = parseModuleSpecifier();
        } else {

            if (match('{')) {
                specifiers = specifiers.concat(parseNamedImports());
            } else if (match('*')) {
                specifiers.push(parseImportNamespaceSpecifier());
            } else if (isIdentifierName(lookahead) && !matchKeyword('default')) {
                specifiers.push(parseImportDefaultSpecifier());
                if (match(',')) {
                    lex();
                    if (match('*')) {
                        specifiers.push(parseImportNamespaceSpecifier());
                    } else if (match('{')) {
                        specifiers = specifiers.concat(parseNamedImports());
                    } else {
                        throwUnexpectedToken(lookahead);
                    }
                }
            } else {
                throwUnexpectedToken(lex());
            }

            if (!matchContextualKeyword('from')) {
                throwError(lookahead.value ?
                    Messages.UnexpectedToken : Messages.MissingFromClause, lookahead.value);
            }
            lex();
            src = parseModuleSpecifier();
        }

        consumeSemicolon();
        return node.finishImportDeclaration(specifiers, src);
    }


    function parseScriptBody() {
        var statement, body = [], token, directive, firstRestricted;

        while (startIndex < length) {
            token = lookahead;
            if (token.type !== Token.StringLiteral) {
                break;
            }

            statement = parseStatementListItem();
            body.push(statement);
            if (statement.expression.type !== Syntax.Literal) {
                break;
            }
            directive = source.slice(token.start + 1, token.end - 1);
            if (directive === 'use strict') {
                strict = true;
                if (firstRestricted) {
                    tolerateUnexpectedToken(firstRestricted, Messages.StrictOctalLiteral);
                }
            } else {
                if (!firstRestricted && token.octal) {
                    firstRestricted = token;
                }
            }
        }

        while (startIndex < length) {
            statement = parseStatementListItem();
            if (typeof statement === 'undefined') {
                break;
            }
            body.push(statement);
        }
        return body;
    }

    function parseProgram() {
        var body, node;

        peek();
        node = new Node();

        body = parseScriptBody();
        return node.finishProgram(body, state.sourceType);
    }

    function filterTokenLocation() {
        var i, entry, token, tokens = [];

        for (i = 0; i < extra.tokens.length; ++i) {
            entry = extra.tokens[i];
            token = {
                type: entry.type,
                value: entry.value
            };
            if (entry.regex) {
                token.regex = {
                    pattern: entry.regex.pattern,
                    flags: entry.regex.flags
                };
            }
            if (extra.range) {
                token.range = entry.range;
            }
            if (extra.loc) {
                token.loc = entry.loc;
            }
            tokens.push(token);
        }

        extra.tokens = tokens;
    }

    function tokenize(code, options) {
        var toString,
            tokens;

        toString = String;
        if (typeof code !== 'string' && !(code instanceof String)) {
            code = toString(code);
        }

        source = code;
        index = 0;
        lineNumber = (source.length > 0) ? 1 : 0;
        lineStart = 0;
        startIndex = index;
        startLineNumber = lineNumber;
        startLineStart = lineStart;
        length = source.length;
        lookahead = null;
        state = {
            allowIn: true,
            allowYield: true,
            labelSet: {},
            inFunctionBody: false,
            inIteration: false,
            inSwitch: false,
            lastCommentStart: -1,
            curlyStack: []
        };

        extra = {};

        options = options || {};

        options.tokens = true;
        extra.tokens = [];
        extra.tokenize = true;
        extra.openParenToken = -1;
        extra.openCurlyToken = -1;

        extra.range = (typeof options.range === 'boolean') && options.range;
        extra.loc = (typeof options.loc === 'boolean') && options.loc;

        if (typeof options.comment === 'boolean' && options.comment) {
            extra.comments = [];
        }
        if (typeof options.tolerant === 'boolean' && options.tolerant) {
            extra.errors = [];
        }

        try {
            peek();
            if (lookahead.type === Token.EOF) {
                return extra.tokens;
            }

            lex();
            while (lookahead.type !== Token.EOF) {
                try {
                    lex();
                } catch (lexError) {
                    if (extra.errors) {
                        recordError(lexError);
                        break;
                    } else {
                        throw lexError;
                    }
                }
            }

            filterTokenLocation();
            tokens = extra.tokens;
            if (typeof extra.comments !== 'undefined') {
                tokens.comments = extra.comments;
            }
            if (typeof extra.errors !== 'undefined') {
                tokens.errors = extra.errors;
            }
        } catch (e) {
            throw e;
        } finally {
            extra = {};
        }
        return tokens;
    }

    function parse(code, options) {
        var program, toString;

        toString = String;
        if (typeof code !== 'string' && !(code instanceof String)) {
            code = toString(code);
        }

        source = code;
        index = 0;
        lineNumber = (source.length > 0) ? 1 : 0;
        lineStart = 0;
        startIndex = index;
        startLineNumber = lineNumber;
        startLineStart = lineStart;
        length = source.length;
        lookahead = null;
        state = {
            allowIn: true,
            allowYield: true,
            labelSet: {},
            inFunctionBody: false,
            inIteration: false,
            inSwitch: false,
            lastCommentStart: -1,
            curlyStack: [],
            sourceType: 'script'
        };
        strict = false;

        extra = {};
        if (typeof options !== 'undefined') {
            extra.range = (typeof options.range === 'boolean') && options.range;
            extra.loc = (typeof options.loc === 'boolean') && options.loc;
            extra.attachComment = (typeof options.attachComment === 'boolean') && options.attachComment;

            if (extra.loc && options.source !== null && options.source !== undefined) {
                extra.source = toString(options.source);
            }

            if (typeof options.tokens === 'boolean' && options.tokens) {
                extra.tokens = [];
            }
            if (typeof options.comment === 'boolean' && options.comment) {
                extra.comments = [];
            }
            if (typeof options.tolerant === 'boolean' && options.tolerant) {
                extra.errors = [];
            }
            if (extra.attachComment) {
                extra.range = true;
                extra.comments = [];
                extra.bottomRightStack = [];
                extra.trailingComments = [];
                extra.leadingComments = [];
            }
            if (options.sourceType === 'module') {
                state.sourceType = options.sourceType;
                strict = true;
            }
        }

        try {
            program = parseProgram();
            if (typeof extra.comments !== 'undefined') {
                program.comments = extra.comments;
            }
            if (typeof extra.tokens !== 'undefined') {
                filterTokenLocation();
                program.tokens = extra.tokens;
            }
            if (typeof extra.errors !== 'undefined') {
                program.errors = extra.errors;
            }
        } catch (e) {
            throw e;
        } finally {
            extra = {};
        }

        return program;
    }

    exports.version = '2.6.0';

    exports.tokenize = tokenize;

    exports.parse = parse;

    exports.Syntax = (function () {
        var name, types = {};

        if (typeof Object.create === 'function') {
            types = Object.create(null);
        }

        for (name in Syntax) {
            if (Syntax.hasOwnProperty(name)) {
                types[name] = Syntax[name];
            }
        }

        if (typeof Object.freeze === 'function') {
            Object.freeze(types);
        }

        return types;
    }());

}(esprima));