/**
 **      ==============================
 **       O           O      O   OOOO
 **       O           O     O O  O   O
 **       O           O     O O  O   O
 **       OOOO   OOOO O     OOO  OOOO
 **       O   O       O    O   O O   O
 **       O   O       O    O   O O   O
 **       OOOO        OOOO O   O OOOO
 **      ==============================
 **      Dr. Stefan Bosse http://www.bsslab.de
 **
 **      COPYRIGHT: THIS SOFTWARE, EXECUTABLE AND SOURCE CODE IS OWNED
 **                 BY THE AUTHOR(S).
 **                 THIS SOURCE CODE MAY NOT BE COPIED, EXTRACTED,
 **                 MODIFIED, OR OTHERWISE USED IN A CONTEXT
 **                 OUTSIDE OF THE SOFTWARE SYSTEM.
 **
 **    $AUTHORS:     Ankit Kuwadekar, Stefan Bosse
 **    $INITIAL:     (C) jQuery Foundation, Inc. and Contributors
 **    $MODIFIED:    (C) 2006-2017 bLAB by sbosse
 **    $Id: estprima.js,v 1.1 2017/06/10 17:03:04 sbosse Exp $
 **    $VERSION:     1.1.4
 **
 **    $INFO:
 **
 ** Esprima JS parser with JST (JavaScript Types) support
 **
 **    $ENDOFINFO
 */

(function (root, factory) {
    'use strict';

    // Universal Module Definition (UMD) to support AMD, CommonJS/Node.js,
    // Rhino, and plain browser loading.

    /* istanbul ignore next */
    if (typeof define === 'function' && define.amd) {
        define(['exports'], factory);
    } else if (typeof exports !== 'undefined') {
        factory(exports);
    } else {
        factory((root.esprima = {}));
    }
}(this, function (exports) {
    'use strict';

    var Token,
        TokenName,
        TypeFlag,
        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
    };

    // JST
    TypeFlag = {    
      TypeBuiltin:'TypeBuiltin',
      TypeUser:'TypeUser',
      TypePoly:'TypePoly',
      TypeLabel:'TypeLabel'
    };
    
    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';

    // A function following one of those tokens is an expression.
    FnExprTokens = ['(', '{', '[', 'in', 'typeof', 'instanceof', 'new',
                    'return', 'case', 'delete', 'throw', 'void',
                    // assignment operators
                    '=', '+=', '-=', '*=', '/=', '%=', '<<=', '>>=', '>>>=',
                    '&=', '|=', '^=', ',',
                    // binary/unary operators
                    '+', '-', '*', '/', '%', '++', '--', '<<', '>>', '>>>', '&',
                    '|', '^', '!', '~', '&&', '||', '?', ':', '===', '==', '>=',
                    '<=', '<', '>', '!=', '!=='];

    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',
        ChoiceType: 'ChoiceType',         // JST a | b | c
        CompoundType: 'CompoundType',     // JST number []
        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',
        StructureType: 'StructureType',     // JST {a:t1,b:t2,...} incl. classes
        Super: 'Super',
        SwitchCase: 'SwitchCase',
        SwitchStatement: 'SwitchStatement',
        TaggedTemplateExpression: 'TaggedTemplateExpression',
        TemplateElement: 'TemplateElement',
        TemplateLiteral: 'TemplateLiteral',
        ThisExpression: 'ThisExpression',
        ThrowStatement: 'ThrowStatement',
        TryStatement: 'TryStatement',
        Type:'Type',                                          // JST string number object array boolean <mytype> <label>
        TypeDefinitionStatement: 'TypeDefinitionStatement',   // JST type t
        TypeExpressionStatement: 'TypeExpressionStatement',   // JST x:t
        UnaryExpression: 'UnaryExpression',
        UpdateExpression: 'UpdateExpression',
        VariableDeclaration: 'VariableDeclaration',
        VariableDeclarator: 'VariableDeclarator',
        WhileStatement: 'WhileStatement',
        WithStatement: 'WithStatement',
        YieldExpression: 'YieldExpression'
    };

    PlaceHolders = {
        ArrowParameterPlaceHolder: 'ArrowParameterPlaceHolder'
    };

    // Error messages should be identical to V8.
    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'
    };

    // See also tools/generate-unicode-regex.js.
    Regex = {
        // ECMAScript 6/Unicode v7.0.0 NonAsciiIdentifierStart:
        NonAsciiIdentifierStart: /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u05D0-\u05EA\u05F0-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u08A0-\u08B2\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58\u0C59\u0C60\u0C61\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D60\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F4\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1877\u1880-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19C1-\u19C7\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1CE9-\u1CEC\u1CEE-\u1CF1\u1CF5\u1CF6\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2118-\u211D\u2124\u2126\u2128\u212A-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303C\u3041-\u3096\u309B-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FCC\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6EF\uA717-\uA71F\uA722-\uA788\uA78B-\uA78E\uA790-\uA7AD\uA7B0\uA7B1\uA7F7-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB5F\uAB64\uAB65\uABC0-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDE80-\uDE9C\uDEA0-\uDED0\uDF00-\uDF1F\uDF30-\uDF4A\uDF50-\uDF75\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00\uDE10-\uDE13\uDE15-\uDE17\uDE19-\uDE33\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE4\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48]|\uD804[\uDC03-\uDC37\uDC83-\uDCAF\uDCD0-\uDCE8\uDD03-\uDD26\uDD50-\uDD72\uDD76\uDD83-\uDDB2\uDDC1-\uDDC4\uDDDA\uDE00-\uDE11\uDE13-\uDE2B\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]/,

        // ECMAScript 6/Unicode v7.0.0 NonAsciiIdentifierPart:
        NonAsciiIdentifierPart: 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uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDDFD\uDE80-\uDE9C\uDEA0-\uDED0\uDEE0\uDF00-\uDF1F\uDF30-\uDF4A\uDF50-\uDF7A\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDCA0-\uDCA9\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00-\uDE03\uDE05\uDE06\uDE0C-\uDE13\uDE15-\uDE17\uDE19-\uDE33\uDE38-\uDE3A\uDE3F\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE6\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48]|\uD804[\uDC00-\uDC46\uDC66-\uDC6F\uDC7F-\uDCBA\uDCD0-\uDCE8\uDCF0-\uDCF9\uDD00-\uDD34\uDD36-\uDD3F\uDD50-\uDD73\uDD76\uDD80-\uDDC4\uDDD0-\uDDDA\uDE00-\uDE11\uDE13-\uDE37\uDEB0-\uDEEA\uDEF0-\uDEF9\uDF01-\uDF03\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3C-\uDF44\uDF47\uDF48\uDF4B-\uDF4D\uDF57\uDF5D-\uDF63\uDF66-\uDF6C\uDF70-\uDF74]|\uD805[\uDC80-\uDCC5\uDCC7\uDCD0-\uDCD9\uDD80-\uDDB5\uDDB8-\uDDC0\uDE00-\uDE40\uDE44\uDE50-\uDE59\uDE80-\uDEB7\uDEC0-\uDEC9]|\uD806[\uDCA0-\uDCE9\uDCFF\uDEC0-\uDEF8]|\uD808[\uDC00-\uDF98]|\uD809[\uDC00-\uDC6E]|[\uD80C\uD840-\uD868\uD86A-\uD86C][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDE60-\uDE69\uDED0-\uDEED\uDEF0-\uDEF4\uDF00-\uDF36\uDF40-\uDF43\uDF50-\uDF59\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDF00-\uDF44\uDF50-\uDF7E\uDF8F-\uDF9F]|\uD82C[\uDC00\uDC01]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99\uDC9D\uDC9E]|\uD834[\uDD65-\uDD69\uDD6D-\uDD72\uDD7B-\uDD82\uDD85-\uDD8B\uDDAA-\uDDAD\uDE42-\uDE44]|\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\uDFCE-\uDFFF]|\uD83A[\uDC00-\uDCC4\uDCD0-\uDCD6]|\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]|\uDB40[\uDD00-\uDDEF]/
    };

    // Ensure the condition is true, otherwise throw an error.
    // This is only to have a better contract semantic, i.e. another safety net
    // to catch a logic error. The condition shall be fulfilled in normal case.
    // Do NOT use this to enforce a certain condition on any user input.

    function assert(condition, message) {
        /* istanbul ignore if */
        if (!condition) {
            throw new Error('ASSERT: ' + message);
        }
    }
    
    function isArray (o) {
      return typeof o == "array" || (typeof o == "object" && o.constructor === Array);
    }

    function isDecimalDigit(ch) {
        return (ch >= 0x30 && ch <= 0x39);   // 0..9
    }

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

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

    function octalToDecimal(ch) {
        // \0 is not octal escape sequence
        var octal = (ch !== '0'), code = '01234567'.indexOf(ch);

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

            // 3 digits are only allowed when string starts
            // with 0, 1, 2, 3
            if ('0123'.indexOf(ch) >= 0 &&
                    index < length &&
                    isOctalDigit(source[index])) {
                code = code * 8 + '01234567'.indexOf(source[index++]);
            }
        }

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

    // ECMA-262 11.2 White Space

    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);
    }

    // ECMA-262 11.3 Line Terminators

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

    // ECMA-262 11.6 Identifier Names and Identifiers

    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) ||  // $ (dollar) and _ (underscore)
            (ch >= 0x41 && ch <= 0x5A) ||         // A..Z
            (ch >= 0x61 && ch <= 0x7A) ||         // a..z
            (ch === 0x5C) ||                      // \ (backslash)
            ((ch >= 0x80) && Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch)));
    }

    function isIdentifierPart(ch) {
        return (ch === 0x24) || (ch === 0x5F) ||  // $ (dollar) and _ (underscore)
            (ch >= 0x41 && ch <= 0x5A) ||         // A..Z
            (ch >= 0x61 && ch <= 0x7A) ||         // a..z
            (ch >= 0x30 && ch <= 0x39) ||         // 0..9
            (ch === 0x5C) ||                      // \ (backslash)
            ((ch >= 0x80) && Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch)));
    }

    // ECMA-262 11.6.2.2 Future Reserved Words

    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';
    }

    // ECMA-262 11.6.2.1 Keywords

    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') || 
                   (id === 'type');   // JST
        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 last (array) {
      return array.length?array[array.length-1]:none;
    }

    function stack () {
      this.data=[];
    }
    stack.prototype.empty = function () {
      return this.data.length==0;
    }
    stack.prototype.last = function () {
      return last(this.data);
    }
    stack.prototype.nth = function (n) {
      return this.data[n-1];
    }
    stack.prototype.parent = function (level) {
      return this.data[level||1];
    }
    stack.prototype.pop = function () {
      var element=this.data[0];
      this.data.shift();
      return element;
    }
    stack.prototype.push = function (element) {
      this.data.unshift(element);
    }
    stack.prototype.top = function () {
      return this.data[0];
    }
    stack.prototype.within = function (type,level) {
      if (level==undefined || level<1) level=0; else level--;
      return this.data[level] && this.data[level].type==type;
    }
    
    // ECMA-262 11.4 Comments

    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);
        }
        if (extra.tokenize) {
            comment.type = comment.type + 'Comment';
            if (extra.delegate) {
                comment = extra.delegate(comment);
            }
            extra.tokens.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) {
                // Block comment ends with '*/'.
                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;
            }
        }

        // Ran off the end of the file - the whole thing is a comment
        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) { // U+002F is '/'
                ch = source.charCodeAt(index + 1);
                if (ch === 0x2F) {
                    ++index;
                    ++index;
                    skipSingleLineComment(2);
                    start = true;
                } else if (ch === 0x2A) {  // U+002A is '*'
                    ++index;
                    ++index;
                    skipMultiLineComment();
                } else {
                    break;
                }
            } else if (start && ch === 0x2D) { // U+002D is '-'
                // U+003E is '>'
                if ((source.charCodeAt(index + 1) === 0x2D) && (source.charCodeAt(index + 2) === 0x3E)) {
                    // '-->' is a single-line comment
                    index += 3;
                    skipSingleLineComment(3);
                } else {
                    break;
                }
            } else if (ch === 0x3C) { // U+003C is '<'
                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;

        // At least, one hex digit is required.
        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;

        // '\u' (U+005C, U+0075) denotes an escaped character.
        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;

            // '\u' (U+005C, U+0075) denotes an escaped character.
            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) {
                // Blackslash (U+005C) marks Unicode escape sequence.
                index = start;
                return getComplexIdentifier();
            } else if (ch >= 0xD800 && ch < 0xDFFF) {
                // Need to handle surrogate pairs.
                index = start;
                return getComplexIdentifier();
            }
            if (isIdentifierPart(ch)) {
                ++index;
            } else {
                break;
            }
        }

        return source.slice(start, index);
    }

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

        start = index;

        // Backslash (U+005C) starts an escaped character.
        id = (source.charCodeAt(index) === 0x5C) ? getComplexIdentifier() : getIdentifier();

        // There is no keyword or literal with only one character.
        // Thus, it must be an identifier.
        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
        };
    }


    // ECMA-262 11.7 Punctuators

    function scanPunctuator() {
        var token, str;

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

        // Check for most common single-character punctuators.
        str = source[index];
        switch (str) {

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

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

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

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

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

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

                    // 2-character punctuators.
                    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 {

                        // 1-character punctuators.
                        str = source[index];
                        if ('<>=!+-*%&|^/'.indexOf(str) >= 0) {
                            ++index;
                        }
                    }
                }
            }
        }

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

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

    // ECMA-262 11.8.3 Numeric Literals

    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) {
            // only 0b or 0B
            throwUnexpectedToken();
        }

        if (index < length) {
            ch = source.charCodeAt(index);
            /* istanbul ignore else */
            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) {
            // only 0o or 0O
            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;

        // Implicit octal, unless there is a non-octal digit.
        // (Annex B.1.1 on Numeric Literals)
        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];

            // Hex number starts with '0x'.
            // Octal number starts with '0'.
            // Octal number in ES6 starts with '0o'.
            // Binary number in ES6 starts with '0b'.
            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
        };
    }

    // ECMA-262 11.8.4 String Literals

    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
        };
    }

    // ECMA-262 11.8.6 Template Literal Lexical Components

    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))) {
                                // Illegal: \01 \02 and so on
                                throwError(Messages.TemplateOctalLiteral);
                            }
                            cooked += '\0';
                        } else if (isOctalDigit(ch)) {
                            // Illegal: \1 \2
                            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
        };
    }

    // ECMA-262 11.8.5 Regular Expression Literals

    function testRegExp(pattern, flags) {
        // The BMP character to use as a replacement for astral symbols when
        // translating an ES6 "u"-flagged pattern to an ES5-compatible
        // approximation.
        // Note: replacing with '\uFFFF' enables false positives in unlikely
        // scenarios. For example, `[\u{1044f}-\u{10440}]` is an invalid
        // pattern that would not be detected by this substitution.
        var astralSubstitute = '\uFFFF',
            tmp = pattern;

        if (flags.indexOf('u') >= 0) {
            tmp = tmp
                // Replace every Unicode escape sequence with the equivalent
                // BMP character or a constant ASCII code point in the case of
                // astral symbols. (See the above note on `astralSubstitute`
                // for more information.)
                .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 each paired surrogate with a single ASCII symbol to
                // avoid throwing on regular expressions that are only valid in
                // combination with the "u" flag.
                .replace(
                    /[\uD800-\uDBFF][\uDC00-\uDFFF]/g,
                    astralSubstitute
                );
        }

        // First, detect invalid regular expressions.
        try {
            RegExp(tmp);
        } catch (e) {
            throwUnexpectedToken(null, Messages.InvalidRegExp);
        }

        // Return a regular expression object for this pattern-flag pair, or
        // `null` in case the current environment doesn't support the flags it
        // uses.
        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++];
                // ECMA-262 7.8.5
                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);
        }

        // Exclude leading and trailing slash.
        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
        };

        /* istanbul ignore next */
        if (!extra.tokenize) {
            // Pop the previous token, which is likely '/' or '/='
            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;
    }

    // Using the following algorithm:
    // https://github.com/mozilla/sweet.js/wiki/design

    function advanceSlash() {
        var regex, previous, check;

        function testKeyword(value) {
            return value && (value.length > 1) && (value[0] >= 'a') && (value[0] <= 'z');
        }

        previous = extra.tokenValues[extra.tokens.length - 1];
        regex = (previous !== null);

        switch (previous) {
        case 'this':
        case ']':
            regex = false;
            break;

        case ')':
            check = extra.tokenValues[extra.openParenToken - 1];
            regex = (check === 'if' || check === 'while' || check === 'for' || check === 'with');
            break;

        case '}':
            // Dividing a function by anything makes little sense,
            // but we have to check for that.
            regex = false;
            if (testKeyword(extra.tokenValues[extra.openCurlyToken - 3])) {
                // Anonymous function, e.g. function(){} /42
                check = extra.tokenValues[extra.openCurlyToken - 4];
                regex = check ? (FnExprTokens.indexOf(check) < 0) : false;
            } else if (testKeyword(extra.tokenValues[extra.openCurlyToken - 4])) {
                // Named function, e.g. function f(){} /42/
                check = extra.tokenValues[extra.openCurlyToken - 5];
                regex = check ? (FnExprTokens.indexOf(check) < 0) : true;
            }
        }

        return regex ? collectRegex() : 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;
        }

        // Very common: ( and ) and ;
        if (cp === 0x28 || cp === 0x29 || cp === 0x3B) {
            return scanPunctuator();
        }

        // String literal starts with single quote (U+0027) or double quote (U+0022).
        if (cp === 0x27 || cp === 0x22) {
            return scanStringLiteral();
        }

        // Dot (.) U+002E can also start a floating-point number, hence the need
        // to check the next character.
        if (cp === 0x2E) {
            if (isDecimalDigit(source.charCodeAt(index + 1))) {
                return scanNumericLiteral();
            }
            return scanPunctuator();
        }

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

        // Slash (/) U+002F can also start a regex.
        if (extra.tokenize && cp === 0x2F) {
            return advanceSlash();
        }

        // Template literals start with ` (U+0060) for template head
        // or } (U+007D) for template middle or template tail.
        if (cp === 0x60 || (cp === 0x7D && state.curlyStack[state.curlyStack.length - 1] === '${')) {
            return scanTemplate();
        }

        // Possible identifier start in a surrogate pair.
        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
                };
            }
            if (extra.tokenValues) {
                extra.tokenValues.push((entry.type === 'Punctuator' || entry.type === 'Keyword') ? entry.value : null);
            }
            if (extra.tokenize) {
                if (!extra.range) {
                    delete entry.range;
                }
                if (!extra.loc) {
                    delete entry.loc;
                }
                if (extra.delegate) {
                    entry = extra.delegate(entry);
                }
            }
            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,
                innerComments,
                leadingComments,
                trailingComments,
                bottomRight = extra.bottomRightStack,
                i,
                comment,
                last = bottomRight[bottomRight.length - 1];

            if (this.type === Syntax.Program) {
                if (this.body.length > 0) {
                    return;
                }
            }
            /**
             * patch innnerComments for properties empty block
             * `function a() {/** comments **\/}`
             */

            if (this.type === Syntax.BlockStatement && this.body.length === 0) {
                innerComments = [];
                for (i = extra.leadingComments.length - 1; i >= 0; --i) {
                    comment = extra.leadingComments[i];
                    if (this.range[1] >= comment.range[1]) {
                        innerComments.unshift(comment);
                        extra.leadingComments.splice(i, 1);
                        extra.trailingComments.splice(i, 1);
                    }
                }
                if (innerComments.length) {
                    this.innerComments = innerComments;
                    //bottomRight.push(this);
                    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;
                }
            }

            // Eating the stack.
            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;
        },

        finishChoiceType: function (choices) {
            this.type = Syntax.ChoiceType;
            this.choices = choices;
            this.finish();
            return this;
        },

        finishCompoundType: function (elements) {
            this.type = Syntax.CompoundType;
            this.elements = elements;
            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;
        },

        finishStructureType: function (elements,name) {
            this.type = Syntax.StructureType;
            this.elements = elements;
            if (name) this.name=name;
            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;
        },

        finishType: function (name,flag) {
            this.type = Syntax.Type;
            this.name = name;
            if (flag) this.flag=flag;
            this.finish();
            return this;
        },

        finishTypeExpressionStatement: function (expression,name) {
            this.type = Syntax.TypeExpressionStatement;
            this.expression = expression;
            if (name) this.name = name;
            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, type) {
            this.type = Syntax.VariableDeclarator;
            this.id = id;
            this.init = init;
            this.Type = type;
            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];
            // Prevent duplicated error.
            /* istanbul ignore next */
            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) {
            /* istanbul ignore else */
            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;
    }

    // Throw an exception

    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);
        /* istanbul ignore next */
        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;
        }
    }

    // Throw an exception because of the token.

    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;
        }
    }

    // Expect the next token to match the specified punctuator.
    // If not, an exception will be thrown.

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

    /**
     * @name expectCommaSeparator
     * @description Quietly expect a comma when in tolerant mode, otherwise delegates
     * to <code>expect(value)</code>
     * @since 2.0
     */
    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(',');
        }
    }

    // Expect the next token to match the specified keyword.
    // If not, an exception will be thrown.

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

    // Return true if the next token matches the specified punctuator.

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

    // Return true if the next token matches the specified keyword

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

    // Return true if the next token matches the specified contextual keyword
    // (where an identifier is sometimes a keyword depending on the context)

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

    // Return true if the next token is an assignment operator

    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() {
        // Catch the very common case first: immediately a semicolon (U+003B).
        if (source.charCodeAt(startIndex) === 0x3B || match(';')) {
            lex();
            return;
        }

        if (hasLineTerminator) {
            return;
        }

        // FIXME(ikarienator): this is seemingly an issue in the previous location info convention.
        lastIndex = startIndex;
        lastLineNumber = startLineNumber;
        lastLineStart = startLineStart;

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

    // Cover grammar support.
    //
    // When an assignment expression position starts with an left parenthesis, the determination of the type
    // of the syntax is to be deferred arbitrarily long until the end of the parentheses pair (plus a lookahead)
    // or the first comma. This situation also defers the determination of all the expressions nested in the pair.
    //
    // There are three productions that can be parsed in a parentheses pair that needs to be determined
    // after the outermost pair is closed. They are:
    //
    //   1. AssignmentExpression
    //   2. BindingElements
    //   3. AssignmentTargets
    //
    // In order to avoid exponential backtracking, we use two flags to denote if the production can be
    // binding element or assignment target.
    //
    // The three productions have the relationship:
    //
    //   BindingElements ⊆ AssignmentTargets ⊆ AssignmentExpression
    //
    // with a single exception that CoverInitializedName when used directly in an Expression, generates
    // an early error. Therefore, we need the third state, firstCoverInitializedNameError, to track the
    // first usage of CoverInitializedName and report it when we reached the end of the parentheses pair.
    //
    // isolateCoverGrammar function runs the given parser function with a new cover grammar context, and it does not
    // effect the current flags. This means the production the parser parses is only used as an expression. Therefore
    // the CoverInitializedName check is conducted.
    //
    // inheritCoverGrammar function runs the given parse function with a new cover grammar context, and it propagates
    // the flags outside of the parser. This means the production the parser parses is used as a part of a potential
    // pattern. The CoverInitializedName check is deferred.
    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;
    }

    // ECMA-262 13.3.3 Destructuring Binding Patterns

    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;
    }

    // ECMA-262 12.2.5 Array Initializer

    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);
    }

    // ECMA-262 12.2.6 Object Initializer

    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();

        // Note: This function is called only from parseObjectProperty(), where
        // EOF and Punctuator tokens are already filtered out.

        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;
    }

    // This function is to try to parse a MethodDefinition as defined in 14.3. But in the case of object literals,
    // it might be called at a position where there is in fact a short hand identifier pattern or a data property.
    // This can only be determined after we consumed up to the left parentheses.
    //
    // In order to avoid back tracking, it returns `null` if the position is not a MethodDefinition and the caller
    // is responsible to visit other options.
    function tryParseMethodDefinition(token, key, computed, node) {
        var value, options, methodNode, params,
            previousAllowYield = state.allowYield;

        if (token.type === Token.Identifier) {
            // check for `get` and `set`;

            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);
        }

        // Not a MethodDefinition.
        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);
        }

        // Check for duplicated __proto__
        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:
            // Allow other node type for tolerant parsing.
            break;
        }
    }

    // ECMA-262 12.2.9 Template Literals

    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);
    }

    // ECMA-262 12.2.10 The Grouping Operator

    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;
    }


    // ECMA-262 12.2 Primary Expressions

    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;
    }

    // ECMA-262 12.3 Left-Hand-Side Expressions

    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;
    }

    // ECMA-262 12.3.3 The new Operator

    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);
    }

    // ECMA-262 12.3.4 Function Calls

    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;
    }

    // ECMA-262 12.3 Left-Hand-Side Expressions

    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;
    }

    // ECMA-262 12.4 Postfix Expressions

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

        expr = inheritCoverGrammar(parseLeftHandSideExpressionAllowCall);

        if (!hasLineTerminator && lookahead.type === Token.Punctuator) {
            if (match('++') || match('--')) {
                // ECMA-262 11.3.1, 11.3.2
                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;
    }

    // ECMA-262 12.5 Unary Operators

    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);
            // ECMA-262 11.4.4, 11.4.5
            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;
    }

    // ECMA-262 12.6 Multiplicative Operators
    // ECMA-262 12.7 Additive Operators
    // ECMA-262 12.8 Bitwise Shift Operators
    // ECMA-262 12.9 Relational Operators
    // ECMA-262 12.10 Equality Operators
    // ECMA-262 12.11 Binary Bitwise Operators
    // ECMA-262 12.12 Binary Logical Operators

    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) {

            // Reduce: make a binary expression from the three topmost entries.
            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);
            }

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

        // Final reduce to clean-up the stack.
        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;
    }


    // ECMA-262 12.13 Conditional Operator

    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;
    }

    // ECMA-262 14.2 Arrow Function Definitions

    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);
    }

    // ECMA-262 14.4 Yield expression

    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);
    }

    // ECMA-262 12.14 Assignment Operators

    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);
            }

            // ECMA-262 12.1.1
            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;
    }

    // ECMA-262 12.15 Comma Operator

    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;
    }

    /////////////////////////////////////
    // JST Type Expression Parser
    /////////////////////////////////////
    
    function parseTypeExpression() {  
        var s = new stack(),_stack=stack;
        function finish(stack) {
          var node;
          if (stack.within(Syntax.ChoiceType,2)) {
            node=stack.parent();
            node.choices.push(stack.pop());          
          } 
          return stack.last();
        }
        function parse(stack) {
          var token, startToken, node, _node;
          startToken = lookahead;
          token = lookahead;
          console.log(token)
          // console.log(token)
          switch (token.type) {
            case 2: return finish(stack);
            case 3:   // Identifier
              switch (token.value) {
                // Builtin Types
                case 'number':
                case 'string':
                case 'boolean':
                case 'object':
                case 'array':
                  lex();
                  if (stack.empty()) {
                    stack.push(new Node().finishType(token.value,TypeFlag.TypeBuiltin));
                  } else if (stack.within(Syntax.CompoundType)) {
                    node=stack.top();
                    node.elements.push(new Node().finishType(token.value,TypeFlag.TypeBuiltin));
                  } else if (stack.within(Syntax.ChoiceType)) {
                    node=stack.top();
                    _node=new Node().finishType(token.value,TypeFlag.TypeBuiltin);
                    node.choices.push(_node);
                    stack.push(_node);
                  } else if (stack.within(Syntax.StructureType)) {
                    node=stack.top();
                    _node=new Node().finishType(token.value,TypeFlag.TypeBuiltin);
                    node.elements.push(_node);
                    stack.push(_node);
                  } else if (stack.within(Syntax.Type)) {
                    node = new Node().finishCompoundType([stack.pop(),new Node().finishType(token.value,TypeFlag.TypeBuiltin)]);
                    stack.push(node);
                  } 
                  return parse(stack);                  
                  break;             
                default:
                  lex();
                  if (stack.empty()) {
                    stack.push(new Node().finishType(token.value,TypeFlag.TypeUser));
                  } else if (stack.within(Syntax.CompoundType)) {
                    node=stack.top();
                    node.elements.push(new Node().finishType(token.value,TypeFlag.TypeUser));
                  } else if (stack.within(Syntax.ChoiceType)) {
                    node=stack.top();
                    _node=new Node().finishType(token.value,TypeFlag.TypeUser);
                    node.choices.push();
                    stack.push(_node);
                  } else if (stack.within(Syntax.StructureType)) {
                    node=stack.top();
                    _node=new Node().finishType(token.value,match(':')?TypeFlag.TypeUser:TypeFlag.TypeLabel);
                    node.elements.push(_node);
                    stack.push(_node);
                  } else if (stack.within(Syntax.Type)) {
                    node = new Node().finishCompoundType([stack.pop(),new Node().finishType(token.value,TypeFlag.TypeUser)]);
                    stack.push(node);
                  } 
                  return parse(stack);                  
                  break
              }
            case 7:
              switch (token.value) {
                case '[':
                  lex();
                  if (match(']')) {
                    lex();
                    if (stack.empty()) {
                      node=new Node().finishType('array',TypeFlag.TypeBuiltin);
                      stack.push(node);
                    } else if (stack.within(Syntax.CompoundType)) {
                      node=stack.top();
                      node.elements.push(new Node().finishType('array',TypeFlag.TypeBuiltin));
                    } else if (stack.within(Syntax.Type)) {
                      node = new Node().finishCompoundType([stack.pop(),new Node().finishType('array',TypeFlag.TypeBuiltin)]);
                      stack.push(node);
                    } 
                  } else expect(']');
                  return parse(stack);
                  break;
                case '{':
                  lex();
                  if (match('}')) {
                    lex();
                    if (stack.empty()) {
                      node=new Node().finishType('object',TypeFlag.TypeBuiltin);
                      stack.push(node);
                    } else if (stack.within(Syntax.CompoundType)) {
                      node=stack.top();
                      node.elements.push(new Node().finishType('object',TypeFlag.TypeBuiltin));
                    } else if (stack.within(Syntax.Type)) {
                      node = new Node().finishCompoundType([stack.pop(),new Node().finishType('object',TypeFlag.TypeBuiltin)]);
                      stack.push(node);
                    } 
                  } else {
                    if (stack.empty()) {
                      node=new Node().finishStructureType([]);
                      stack.push(node);
                    }
                  }
                  return parse(stack);
                  break;
                case '}':
                  lex();
                  if (stack.within(Syntax.StructureType,2)) {stack.pop();}
                  break;
                case ':':
                  lex();
                  if (!stack.within(Syntax.StructureType,2)) {} //error
                  else if (stack.within(Syntax.Type)) {
                    _node = stack.pop();
                    node = new Node().finishTypeExpressionStatement(parse(new _stack()),_node.name);
                    stack.top().elements[stack.top().elements.length-1]=node;
                    stack.push(node);
                  }                  
                  return parse(stack);
                  break;
                case '*':
                  lex();
                  if (stack.empty()) {
                    stack.push(new Node().finishType('any',TypeFlag.TypePoly));
                  } else if (stack.within(Syntax.CompoundType)) {
                    node=stack.top();
                    node.elements.push(new Node().finishType('any'));
                  } else if (stack.within(Syntax.ChoiceType)) {
                    node=stack.top();
                    _node=new Node().finishType('any',TypeFlag.TypePoly);
                    node.choices.push();
                    stack.push(_node);
                  } else if (stack.within(Syntax.StructureType)) {
                    node=stack.top();
                    _node=new Node().finishType('any',TypeFlag.TypePoly);
                    node.elements.push(_node);
                    stack.push(_node);
                  } else if (stack.within(Syntax.Type)) {
                    node = new Node().finishCompoundType([stack.pop(),new Node().finishType('any',TypeFlag.TypePoly)]);
                    stack.push(node);
                  } 
                  return parse(stack);
                  break;
                case '|':
                  lex();
                  if (stack.empty()) {
                    //error
                  } else if (stack.within(Syntax.CompoundType) ||
                             stack.within(Syntax.Type)) {
                    if (stack.within(Syntax.ChoiceType,2)) {
                      stack.pop();
                    } else {
                      node = new Node().finishChoiceType([stack.pop()]);
                      stack.push(node);
                    }
                  }
                  return parse(stack);
                  break;
                case ',':
                  if (stack.empty()) {
                    // error
                  } else if (stack.within(Syntax.CompoundType) ||
                             stack.within(Syntax.Type) ||
                             stack.within(Syntax.TypeExpressionStatement)) {
                    if (stack.within(Syntax.StructureType,2)) {
                      stack.pop();
                    } 
                    // else {
                    //  node = new Node().finishStructureType([stack.pop()]);
                    //  stack.push(node);
                    else
                      return finish(stack);
                  }
                  lex();
                  return parse(stack);
                  break;
                default:
                  return finish(stack);
                  break;
              }
            default:
              return finish(stack);
          }
          return finish(stack);
        }
        return new Node().finishTypeExpressionStatement(parse(s));
    }

    // ECMA-262 13.2 Block

    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);
    }

    // ECMA-262 13.3.2 Variable Statement

    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, type = null, id, node = new Node(), params = [];

        id = parsePattern(params, 'var');

        // ECMA-262 12.2.1
        if (strict && isRestrictedWord(id.name)) {
            tolerateError(Messages.StrictVarName);
        }

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

        return node.finishVariableDeclarator(id, init, type);
    }

    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);
    }

    // ECMA-262 13.3.1 Let and Const Declarations

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

        id = parsePattern(params, kind);

        // ECMA-262 12.2.1
        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);
    }

    // ECMA-262 13.4 Empty Statement

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

    // ECMA-262 12.4 Expression Statement

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

    // ECMA-262 13.6 If statement

    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);
    }

    // ECMA-262 13.7 Iteration Statements

    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;

                if (!strict && lookahead.value === 'in') {
                    init = init.finishIdentifier(kind);
                    lex();
                    left = init;
                    right = parseExpression();
                    init = null;
                } else {
                    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;

        return (typeof left === 'undefined') ?
                node.finishForStatement(init, test, update, body) :
                forIn ? node.finishForInStatement(left, right, body) :
                    node.finishForOfStatement(left, right, body);
    }

    // ECMA-262 13.8 The continue statement

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

        expectKeyword('continue');

        // Optimize the most common form: '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);
    }

    // ECMA-262 13.9 The break statement

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

        expectKeyword('break');

        // Catch the very common case first: immediately a semicolon (U+003B).
        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);
    }

    // ECMA-262 13.10 The return statement

    function parseReturnStatement(node) {
        var argument = null;

        expectKeyword('return');

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

        // 'return' followed by a space and an identifier is very common.
        if (source.charCodeAt(lastIndex) === 0x20) {
            if (isIdentifierStart(source.charCodeAt(lastIndex + 1))) {
                argument = parseExpression();
                consumeSemicolon();
                return node.finishReturnStatement(argument);
            }
        }

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

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

        consumeSemicolon();

        return node.finishReturnStatement(argument);
    }

    // ECMA-262 13.11 The with statement

    function parseWithStatement(node) {
        var object, body;

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

        expectKeyword('with');

        expect('(');

        object = parseExpression();

        expect(')');

        body = parseStatement();

        return node.finishWithStatement(object, body);
    }

    // ECMA-262 13.12 The switch statement

    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);
    }

    // ECMA-262 13.14 The throw statement

    function parseThrowStatement(node) {
        var argument;

        expectKeyword('throw');

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

        argument = parseExpression();

        consumeSemicolon();

        return node.finishThrowStatement(argument);
    }

    // ECMA-262 13.15 The try statement

    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;
        }

        // ECMA-262 12.14.1
        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);
    }

    // ECMA-262 13.16 The debugger statement

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

        consumeSemicolon();

        return node.finishDebuggerStatement();
    }

    // 13 Statements

    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();

        // ECMA-262 12.12 Labelled Statements
        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);
    }

    // ECMA-262 14.1 Function Definition

    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) {
                // this is not directive
                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)) {
                  last(options.params).Type=new Node().finishType('any',TypeFlag.TypePoly);
                  break;
                }
                // JST
                if (match(':')) {
                  lex();
                  last(options.params).Type=parseTypeExpression();
                  if (match(')')) break;
                } else last(options.params).Type=new Node().finishType('any',TypeFlag.TypePoly);
                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);
    }

    // ECMA-262 14.5 Class Definitions

    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; // jscs:ignore requireDotNotation
                    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);
    }

    // ECMA-262 15.2 Modules

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

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

    // ECMA-262 15.2.3 Exports

    function parseExportSpecifier() {
        var exported, local, node = new Node(), def;
        if (matchKeyword('default')) {
            // export {default} from 'something';
            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 = [];

        // non-default export
        if (lookahead.type === Token.Keyword) {
            // covers:
            // export var f = 1;
            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')) {
            // covering:
            // export {default} from 'foo';
            // export {foo} from 'foo';
            lex();
            src = parseModuleSpecifier();
            consumeSemicolon();
        } else if (isExportFromIdentifier) {
            // covering:
            // export {default}; // missing fromClause
            throwError(lookahead.value ?
                    Messages.UnexpectedToken : Messages.MissingFromClause, lookahead.value);
        } else {
            // cover
            // export {foo};
            consumeSemicolon();
        }
        return node.finishExportNamedDeclaration(declaration, specifiers, src);
    }

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

        // covers:
        // export default ...
        expectKeyword('default');

        if (matchKeyword('function')) {
            // covers:
            // export default function foo () {}
            // export default 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);
        }

        // covers:
        // export default {};
        // export default [];
        // export default (1 + 2);
        if (match('{')) {
            expression = parseObjectInitializer();
        } else if (match('[')) {
            expression = parseArrayInitializer();
        } else {
            expression = parseAssignmentExpression();
        }
        consumeSemicolon();
        return node.finishExportDefaultDeclaration(expression);
    }

    function parseExportAllDeclaration(node) {
        var src;

        // covers:
        // export * from 'foo';
        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);
    }

    // ECMA-262 15.2.2 Imports

    function parseImportSpecifier() {
        // import {<foo as bar>} ...;
        var local, imported, node = new Node();

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

        return node.finishImportSpecifier(local, imported);
    }

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

    function parseImportDefaultSpecifier() {
        // import <foo> ...;
        var local, node = new Node();

        local = parseNonComputedProperty();

        return node.finishImportDefaultSpecifier(local);
    }

    function parseImportNamespaceSpecifier() {
        // import <* as foo> ...;
        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) {
            // import 'foo';
            src = parseModuleSpecifier();
        } else {

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

    // ECMA-262 15.1 Scripts

    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) {
                // this is not directive
                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();
            /* istanbul ignore if */
            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, delegate) {
        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 matching.
        options = options || {};

        // Of course we collect tokens here.
        options.tokens = true;
        extra.tokens = [];
        extra.tokenValues = [];
        extra.tokenize = true;
        extra.delegate = delegate;

        // The following two fields are necessary to compute the Regex tokens.
        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);
                        // We have to break on the first error
                        // to avoid infinite loops.
                        break;
                    } else {
                        throw lexError;
                    }
                }
            }

            tokens = extra.tokens;
            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') {
                // very restrictive condition for now
                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;
    }

    // Sync with *.json manifests.
    exports.version = '2.7.0';

    exports.tokenize = tokenize;

    exports.parse = parse;

    // Deep copy.
    /* istanbul ignore next */
    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;
    }());

}));
/* vim: set sw=4 ts=4 et tw=80 : */