demo/typescript.js
function createScanner(languageVersion, skipTrivia, languageVariant, text, onError, start, length) {
        if (languageVariant === void 0) { languageVariant = 0 /* Standard */; }
        // Current position (end position of text of current token)
        var pos;
        // end of text
        var end;
        // Start position of whitespace before current token
        var startPos;
        // Start position of text of current token
        var tokenPos;
        var token;
        var tokenValue;
        var precedingLineBreak;
        var hasExtendedUnicodeEscape;
        var tokenIsUnterminated;
        setText(text, start, length);
        return {
            getStartPos: function () { return startPos; },
            getTextPos: function () { return pos; },
            getToken: function () { return token; },
            getTokenPos: function () { return tokenPos; },
            getTokenText: function () { return text.substring(tokenPos, pos); },
            getTokenValue: function () { return tokenValue; },
            hasExtendedUnicodeEscape: function () { return hasExtendedUnicodeEscape; },
            hasPrecedingLineBreak: function () { return precedingLineBreak; },
            isIdentifier: function () { return token === 69 /* Identifier */ || token > 105 /* LastReservedWord */; },
            isReservedWord: function () { return token >= 70 /* FirstReservedWord */ && token <= 105 /* LastReservedWord */; },
            isUnterminated: function () { return tokenIsUnterminated; },
            reScanGreaterToken: reScanGreaterToken,
            reScanSlashToken: reScanSlashToken,
            reScanTemplateToken: reScanTemplateToken,
            scanJsxIdentifier: scanJsxIdentifier,
            reScanJsxToken: reScanJsxToken,
            scanJsxToken: scanJsxToken,
            scan: scan,
            setText: setText,
            setScriptTarget: setScriptTarget,
            setLanguageVariant: setLanguageVariant,
            setOnError: setOnError,
            setTextPos: setTextPos,
            tryScan: tryScan,
            lookAhead: lookAhead
        };
        function error(message, length) {
            if (onError) {
                onError(message, length || 0);
            }
        }
        function scanNumber() {
            var start = pos;
            while (isDigit(text.charCodeAt(pos)))
                pos++;
            if (text.charCodeAt(pos) === 46 /* dot */) {
                pos++;
                while (isDigit(text.charCodeAt(pos)))
                    pos++;
            }
            var end = pos;
            if (text.charCodeAt(pos) === 69 /* E */ || text.charCodeAt(pos) === 101 /* e */) {
                pos++;
                if (text.charCodeAt(pos) === 43 /* plus */ || text.charCodeAt(pos) === 45 /* minus */)
                    pos++;
                if (isDigit(text.charCodeAt(pos))) {
                    pos++;
                    while (isDigit(text.charCodeAt(pos)))
                        pos++;
                    end = pos;
                }
                else {
                    error(ts.Diagnostics.Digit_expected);
                }
            }
            return +(text.substring(start, end));
        }
        function scanOctalDigits() {
            var start = pos;
            while (isOctalDigit(text.charCodeAt(pos))) {
                pos++;
            }
            return +(text.substring(start, pos));
        }
        /**
         * Scans the given number of hexadecimal digits in the text,
         * returning -1 if the given number is unavailable.
         */
        function scanExactNumberOfHexDigits(count) {
            return scanHexDigits(/*minCount*/ count, /*scanAsManyAsPossible*/ false);
        }
        /**
         * Scans as many hexadecimal digits as are available in the text,
         * returning -1 if the given number of digits was unavailable.
         */
        function scanMinimumNumberOfHexDigits(count) {
            return scanHexDigits(/*minCount*/ count, /*scanAsManyAsPossible*/ true);
        }
        function scanHexDigits(minCount, scanAsManyAsPossible) {
            var digits = 0;
            var value = 0;
            while (digits < minCount || scanAsManyAsPossible) {
                var ch = text.charCodeAt(pos);
                if (ch >= 48 /* _0 */ && ch <= 57 /* _9 */) {
                    value = value * 16 + ch - 48 /* _0 */;
                }
                else if (ch >= 65 /* A */ && ch <= 70 /* F */) {
                    value = value * 16 + ch - 65 /* A */ + 10;
                }
                else if (ch >= 97 /* a */ && ch <= 102 /* f */) {
                    value = value * 16 + ch - 97 /* a */ + 10;
                }
                else {
                    break;
                }
                pos++;
                digits++;
            }
            if (digits < minCount) {
                value = -1;
            }
            return value;
        }
        function scanString() {
            var quote = text.charCodeAt(pos++);
            var result = "";
            var start = pos;
            while (true) {
                if (pos >= end) {
                    result += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_string_literal);
                    break;
                }
                var ch = text.charCodeAt(pos);
                if (ch === quote) {
                    result += text.substring(start, pos);
                    pos++;
                    break;
                }
                if (ch === 92 /* backslash */) {
                    result += text.substring(start, pos);
                    result += scanEscapeSequence();
                    start = pos;
                    continue;
                }
                if (isLineBreak(ch)) {
                    result += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_string_literal);
                    break;
                }
                pos++;
            }
            return result;
        }
        /**
         * Sets the current 'tokenValue' and returns a NoSubstitutionTemplateLiteral or
         * a literal component of a TemplateExpression.
         */
        function scanTemplateAndSetTokenValue() {
            var startedWithBacktick = text.charCodeAt(pos) === 96 /* backtick */;
            pos++;
            var start = pos;
            var contents = "";
            var resultingToken;
            while (true) {
                if (pos >= end) {
                    contents += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_template_literal);
                    resultingToken = startedWithBacktick ? 11 /* NoSubstitutionTemplateLiteral */ : 14 /* TemplateTail */;
                    break;
                }
                var currChar = text.charCodeAt(pos);
                // '`'
                if (currChar === 96 /* backtick */) {
                    contents += text.substring(start, pos);
                    pos++;
                    resultingToken = startedWithBacktick ? 11 /* NoSubstitutionTemplateLiteral */ : 14 /* TemplateTail */;
                    break;
                }
                // '${'
                if (currChar === 36 /* $ */ && pos + 1 < end && text.charCodeAt(pos + 1) === 123 /* openBrace */) {
                    contents += text.substring(start, pos);
                    pos += 2;
                    resultingToken = startedWithBacktick ? 12 /* TemplateHead */ : 13 /* TemplateMiddle */;
                    break;
                }
                // Escape character
                if (currChar === 92 /* backslash */) {
                    contents += text.substring(start, pos);
                    contents += scanEscapeSequence();
                    start = pos;
                    continue;
                }
                // Speculated ECMAScript 6 Spec 11.8.6.1:
                // <CR><LF> and <CR> LineTerminatorSequences are normalized to <LF> for Template Values
                if (currChar === 13 /* carriageReturn */) {
                    contents += text.substring(start, pos);
                    pos++;
                    if (pos < end && text.charCodeAt(pos) === 10 /* lineFeed */) {
                        pos++;
                    }
                    contents += "\n";
                    start = pos;
                    continue;
                }
                pos++;
            }
            ts.Debug.assert(resultingToken !== undefined);
            tokenValue = contents;
            return resultingToken;
        }
        function scanEscapeSequence() {
            pos++;
            if (pos >= end) {
                error(ts.Diagnostics.Unexpected_end_of_text);
                return "";
            }
            var ch = text.charCodeAt(pos++);
            switch (ch) {
                case 48 /* _0 */:
                    return "\0";
                case 98 /* b */:
                    return "\b";
                case 116 /* t */:
                    return "\t";
                case 110 /* n */:
                    return "\n";
                case 118 /* v */:
                    return "\v";
                case 102 /* f */:
                    return "\f";
                case 114 /* r */:
                    return "\r";
                case 39 /* singleQuote */:
                    return "\'";
                case 34 /* doubleQuote */:
                    return "\"";
                case 117 /* u */:
                    // '\u{DDDDDDDD}'
                    if (pos < end && text.charCodeAt(pos) === 123 /* openBrace */) {
                        hasExtendedUnicodeEscape = true;
                        pos++;
                        return scanExtendedUnicodeEscape();
                    }
                    // '\uDDDD'
                    return scanHexadecimalEscape(/*numDigits*/ 4);
                case 120 /* x */:
                    // '\xDD'
                    return scanHexadecimalEscape(/*numDigits*/ 2);
                // when encountering a LineContinuation (i.e. a backslash and a line terminator sequence),
                // the line terminator is interpreted to be "the empty code unit sequence".
                case 13 /* carriageReturn */:
                    if (pos < end && text.charCodeAt(pos) === 10 /* lineFeed */) {
                        pos++;
                    }
                // fall through
                case 10 /* lineFeed */:
                case 8232 /* lineSeparator */:
                case 8233 /* paragraphSeparator */:
                    return "";
                default:
                    return String.fromCharCode(ch);
            }
        }
        function scanHexadecimalEscape(numDigits) {
            var escapedValue = scanExactNumberOfHexDigits(numDigits);
            if (escapedValue >= 0) {
                return String.fromCharCode(escapedValue);
            }
            else {
                error(ts.Diagnostics.Hexadecimal_digit_expected);
                return "";
            }
        }
        function scanExtendedUnicodeEscape() {
            var escapedValue = scanMinimumNumberOfHexDigits(1);
            var isInvalidExtendedEscape = false;
            // Validate the value of the digit
            if (escapedValue < 0) {
                error(ts.Diagnostics.Hexadecimal_digit_expected);
                isInvalidExtendedEscape = true;
            }
            else if (escapedValue > 0x10FFFF) {
                error(ts.Diagnostics.An_extended_Unicode_escape_value_must_be_between_0x0_and_0x10FFFF_inclusive);
                isInvalidExtendedEscape = true;
            }
            if (pos >= end) {
                error(ts.Diagnostics.Unexpected_end_of_text);
                isInvalidExtendedEscape = true;
            }
            else if (text.charCodeAt(pos) === 125 /* closeBrace */) {
                // Only swallow the following character up if it's a '}'.
                pos++;
            }
            else {
                error(ts.Diagnostics.Unterminated_Unicode_escape_sequence);
                isInvalidExtendedEscape = true;
            }
            if (isInvalidExtendedEscape) {
                return "";
            }
            return utf16EncodeAsString(escapedValue);
        }
        // Derived from the 10.1.1 UTF16Encoding of the ES6 Spec.
        function utf16EncodeAsString(codePoint) {
            ts.Debug.assert(0x0 <= codePoint && codePoint <= 0x10FFFF);
            if (codePoint <= 65535) {
                return String.fromCharCode(codePoint);
            }
            var codeUnit1 = Math.floor((codePoint - 65536) / 1024) + 0xD800;
            var codeUnit2 = ((codePoint - 65536) % 1024) + 0xDC00;
            return String.fromCharCode(codeUnit1, codeUnit2);
        }
        // Current character is known to be a backslash. Check for Unicode escape of the form '\uXXXX'
        // and return code point value if valid Unicode escape is found. Otherwise return -1.
        function peekUnicodeEscape() {
            if (pos + 5 < end && text.charCodeAt(pos + 1) === 117 /* u */) {
                var start_1 = pos;
                pos += 2;
                var value = scanExactNumberOfHexDigits(4);
                pos = start_1;
                return value;
            }
            return -1;
        }
        function scanIdentifierParts() {
            var result = "";
            var start = pos;
            while (pos < end) {
                var ch = text.charCodeAt(pos);
                if (isIdentifierPart(ch, languageVersion)) {
                    pos++;
                }
                else if (ch === 92 /* backslash */) {
                    ch = peekUnicodeEscape();
                    if (!(ch >= 0 && isIdentifierPart(ch, languageVersion))) {
                        break;
                    }
                    result += text.substring(start, pos);
                    result += String.fromCharCode(ch);
                    // Valid Unicode escape is always six characters
                    pos += 6;
                    start = pos;
                }
                else {
                    break;
                }
            }
            result += text.substring(start, pos);
            return result;
        }
        function getIdentifierToken() {
            // Reserved words are between 2 and 11 characters long and start with a lowercase letter
            var len = tokenValue.length;
            if (len >= 2 && len <= 11) {
                var ch = tokenValue.charCodeAt(0);
                if (ch >= 97 /* a */ && ch <= 122 /* z */ && hasOwnProperty.call(textToToken, tokenValue)) {
                    return token = textToToken[tokenValue];
                }
            }
            return token = 69 /* Identifier */;
        }
        function scanBinaryOrOctalDigits(base) {
            ts.Debug.assert(base !== 2 || base !== 8, "Expected either base 2 or base 8");
            var value = 0;
            // For counting number of digits; Valid binaryIntegerLiteral must have at least one binary digit following B or b.
            // Similarly valid octalIntegerLiteral must have at least one octal digit following o or O.
            var numberOfDigits = 0;
            while (true) {
                var ch = text.charCodeAt(pos);
                var valueOfCh = ch - 48 /* _0 */;
                if (!isDigit(ch) || valueOfCh >= base) {
                    break;
                }
                value = value * base + valueOfCh;
                pos++;
                numberOfDigits++;
            }
            // Invalid binaryIntegerLiteral or octalIntegerLiteral
            if (numberOfDigits === 0) {
                return -1;
            }
            return value;
        }
        function scan() {
            startPos = pos;
            hasExtendedUnicodeEscape = false;
            precedingLineBreak = false;
            tokenIsUnterminated = false;
            while (true) {
                tokenPos = pos;
                if (pos >= end) {
                    return token = 1 /* EndOfFileToken */;
                }
                var ch = text.charCodeAt(pos);
                // Special handling for shebang
                if (ch === 35 /* hash */ && pos === 0 && isShebangTrivia(text, pos)) {
                    pos = scanShebangTrivia(text, pos);
                    if (skipTrivia) {
                        continue;
                    }
                    else {
                        return token = 6 /* ShebangTrivia */;
                    }
                }
                switch (ch) {
                    case 10 /* lineFeed */:
                    case 13 /* carriageReturn */:
                        precedingLineBreak = true;
                        if (skipTrivia) {
                            pos++;
                            continue;
                        }
                        else {
                            if (ch === 13 /* carriageReturn */ && pos + 1 < end && text.charCodeAt(pos + 1) === 10 /* lineFeed */) {
                                // consume both CR and LF
                                pos += 2;
                            }
                            else {
                                pos++;
                            }
                            return token = 4 /* NewLineTrivia */;
                        }
                    case 9 /* tab */:
                    case 11 /* verticalTab */:
                    case 12 /* formFeed */:
                    case 32 /* space */:
                        if (skipTrivia) {
                            pos++;
                            continue;
                        }
                        else {
                            while (pos < end && isWhiteSpace(text.charCodeAt(pos))) {
                                pos++;
                            }
                            return token = 5 /* WhitespaceTrivia */;
                        }
                    case 33 /* exclamation */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 33 /* ExclamationEqualsEqualsToken */;
                            }
                            return pos += 2, token = 31 /* ExclamationEqualsToken */;
                        }
                        return pos++, token = 49 /* ExclamationToken */;
                    case 34 /* doubleQuote */:
                    case 39 /* singleQuote */:
                        tokenValue = scanString();
                        return token = 9 /* StringLiteral */;
                    case 96 /* backtick */:
                        return token = scanTemplateAndSetTokenValue();
                    case 37 /* percent */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 62 /* PercentEqualsToken */;
                        }
                        return pos++, token = 40 /* PercentToken */;
                    case 38 /* ampersand */:
                        if (text.charCodeAt(pos + 1) === 38 /* ampersand */) {
                            return pos += 2, token = 51 /* AmpersandAmpersandToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 66 /* AmpersandEqualsToken */;
                        }
                        return pos++, token = 46 /* AmpersandToken */;
                    case 40 /* openParen */:
                        return pos++, token = 17 /* OpenParenToken */;
                    case 41 /* closeParen */:
                        return pos++, token = 18 /* CloseParenToken */;
                    case 42 /* asterisk */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 59 /* AsteriskEqualsToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 42 /* asterisk */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 60 /* AsteriskAsteriskEqualsToken */;
                            }
                            return pos += 2, token = 38 /* AsteriskAsteriskToken */;
                        }
                        return pos++, token = 37 /* AsteriskToken */;
                    case 43 /* plus */:
                        if (text.charCodeAt(pos + 1) === 43 /* plus */) {
                            return pos += 2, token = 41 /* PlusPlusToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 57 /* PlusEqualsToken */;
                        }
                        return pos++, token = 35 /* PlusToken */;
                    case 44 /* comma */:
                        return pos++, token = 24 /* CommaToken */;
                    case 45 /* minus */:
                        if (text.charCodeAt(pos + 1) === 45 /* minus */) {
                            return pos += 2, token = 42 /* MinusMinusToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 58 /* MinusEqualsToken */;
                        }
                        return pos++, token = 36 /* MinusToken */;
                    case 46 /* dot */:
                        if (isDigit(text.charCodeAt(pos + 1))) {
                            tokenValue = "" + scanNumber();
                            return token = 8 /* NumericLiteral */;
                        }
                        if (text.charCodeAt(pos + 1) === 46 /* dot */ && text.charCodeAt(pos + 2) === 46 /* dot */) {
                            return pos += 3, token = 22 /* DotDotDotToken */;
                        }
                        return pos++, token = 21 /* DotToken */;
                    case 47 /* slash */:
                        // Single-line comment
                        if (text.charCodeAt(pos + 1) === 47 /* slash */) {
                            pos += 2;
                            while (pos < end) {
                                if (isLineBreak(text.charCodeAt(pos))) {
                                    break;
                                }
                                pos++;
                            }
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 2 /* SingleLineCommentTrivia */;
                            }
                        }
                        // Multi-line comment
                        if (text.charCodeAt(pos + 1) === 42 /* asterisk */) {
                            pos += 2;
                            var commentClosed = false;
                            while (pos < end) {
                                var ch_2 = text.charCodeAt(pos);
                                if (ch_2 === 42 /* asterisk */ && text.charCodeAt(pos + 1) === 47 /* slash */) {
                                    pos += 2;
                                    commentClosed = true;
                                    break;
                                }
                                if (isLineBreak(ch_2)) {
                                    precedingLineBreak = true;
                                }
                                pos++;
                            }
                            if (!commentClosed) {
                                error(ts.Diagnostics.Asterisk_Slash_expected);
                            }
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                tokenIsUnterminated = !commentClosed;
                                return token = 3 /* MultiLineCommentTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 61 /* SlashEqualsToken */;
                        }
                        return pos++, token = 39 /* SlashToken */;
                    case 48 /* _0 */:
                        if (pos + 2 < end && (text.charCodeAt(pos + 1) === 88 /* X */ || text.charCodeAt(pos + 1) === 120 /* x */)) {
                            pos += 2;
                            var value = scanMinimumNumberOfHexDigits(1);
                            if (value < 0) {
                                error(ts.Diagnostics.Hexadecimal_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        else if (pos + 2 < end && (text.charCodeAt(pos + 1) === 66 /* B */ || text.charCodeAt(pos + 1) === 98 /* b */)) {
                            pos += 2;
                            var value = scanBinaryOrOctalDigits(/* base */ 2);
                            if (value < 0) {
                                error(ts.Diagnostics.Binary_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        else if (pos + 2 < end && (text.charCodeAt(pos + 1) === 79 /* O */ || text.charCodeAt(pos + 1) === 111 /* o */)) {
                            pos += 2;
                            var value = scanBinaryOrOctalDigits(/* base */ 8);
                            if (value < 0) {
                                error(ts.Diagnostics.Octal_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        // Try to parse as an octal
                        if (pos + 1 < end && isOctalDigit(text.charCodeAt(pos + 1))) {
                            tokenValue = "" + scanOctalDigits();
                            return token = 8 /* NumericLiteral */;
                        }
                    // This fall-through is a deviation from the EcmaScript grammar. The grammar says that a leading zero
                    // can only be followed by an octal digit, a dot, or the end of the number literal. However, we are being
                    // permissive and allowing decimal digits of the form 08* and 09* (which many browsers also do).
                    case 49 /* _1 */:
                    case 50 /* _2 */:
                    case 51 /* _3 */:
                    case 52 /* _4 */:
                    case 53 /* _5 */:
                    case 54 /* _6 */:
                    case 55 /* _7 */:
                    case 56 /* _8 */:
                    case 57 /* _9 */:
                        tokenValue = "" + scanNumber();
                        return token = 8 /* NumericLiteral */;
                    case 58 /* colon */:
                        return pos++, token = 54 /* ColonToken */;
                    case 59 /* semicolon */:
                        return pos++, token = 23 /* SemicolonToken */;
                    case 60 /* lessThan */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 60 /* lessThan */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 63 /* LessThanLessThanEqualsToken */;
                            }
                            return pos += 2, token = 43 /* LessThanLessThanToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 28 /* LessThanEqualsToken */;
                        }
                        if (languageVariant === 1 /* JSX */ &&
                            text.charCodeAt(pos + 1) === 47 /* slash */ &&
                            text.charCodeAt(pos + 2) !== 42 /* asterisk */) {
                            return pos += 2, token = 26 /* LessThanSlashToken */;
                        }
                        return pos++, token = 25 /* LessThanToken */;
                    case 61 /* equals */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 32 /* EqualsEqualsEqualsToken */;
                            }
                            return pos += 2, token = 30 /* EqualsEqualsToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 62 /* greaterThan */) {
                            return pos += 2, token = 34 /* EqualsGreaterThanToken */;
                        }
                        return pos++, token = 56 /* EqualsToken */;
                    case 62 /* greaterThan */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        return pos++, token = 27 /* GreaterThanToken */;
                    case 63 /* question */:
                        return pos++, token = 53 /* QuestionToken */;
                    case 91 /* openBracket */:
                        return pos++, token = 19 /* OpenBracketToken */;
                    case 93 /* closeBracket */:
                        return pos++, token = 20 /* CloseBracketToken */;
                    case 94 /* caret */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 68 /* CaretEqualsToken */;
                        }
                        return pos++, token = 48 /* CaretToken */;
                    case 123 /* openBrace */:
                        return pos++, token = 15 /* OpenBraceToken */;
                    case 124 /* bar */:
                        if (text.charCodeAt(pos + 1) === 124 /* bar */) {
                            return pos += 2, token = 52 /* BarBarToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 67 /* BarEqualsToken */;
                        }
                        return pos++, token = 47 /* BarToken */;
                    case 125 /* closeBrace */:
                        return pos++, token = 16 /* CloseBraceToken */;
                    case 126 /* tilde */:
                        return pos++, token = 50 /* TildeToken */;
                    case 64 /* at */:
                        return pos++, token = 55 /* AtToken */;
                    case 92 /* backslash */:
                        var cookedChar = peekUnicodeEscape();
                        if (cookedChar >= 0 && isIdentifierStart(cookedChar, languageVersion)) {
                            pos += 6;
                            tokenValue = String.fromCharCode(cookedChar) + scanIdentifierParts();
                            return token = getIdentifierToken();
                        }
                        error(ts.Diagnostics.Invalid_character);
                        return pos++, token = 0 /* Unknown */;
                    default:
                        if (isIdentifierStart(ch, languageVersion)) {
                            pos++;
                            while (pos < end && isIdentifierPart(ch = text.charCodeAt(pos), languageVersion))
                                pos++;
                            tokenValue = text.substring(tokenPos, pos);
                            if (ch === 92 /* backslash */) {
                                tokenValue += scanIdentifierParts();
                            }
                            return token = getIdentifierToken();
                        }
                        else if (isWhiteSpace(ch)) {
                            pos++;
                            continue;
                        }
                        else if (isLineBreak(ch)) {
                            precedingLineBreak = true;
                            pos++;
                            continue;
                        }
                        error(ts.Diagnostics.Invalid_character);
                        return pos++, token = 0 /* Unknown */;
                }
            }
        }
        function reScanGreaterToken() {
            if (token === 27 /* GreaterThanToken */) {
                if (text.charCodeAt(pos) === 62 /* greaterThan */) {
                    if (text.charCodeAt(pos + 1) === 62 /* greaterThan */) {
                        if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                            return pos += 3, token = 65 /* GreaterThanGreaterThanGreaterThanEqualsToken */;
                        }
                        return pos += 2, token = 45 /* GreaterThanGreaterThanGreaterThanToken */;
                    }
                    if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                        return pos += 2, token = 64 /* GreaterThanGreaterThanEqualsToken */;
                    }
                    return pos++, token = 44 /* GreaterThanGreaterThanToken */;
                }
                if (text.charCodeAt(pos) === 61 /* equals */) {
                    return pos++, token = 29 /* GreaterThanEqualsToken */;
                }
            }
            return token;
        }
        function reScanSlashToken() {
            if (token === 39 /* SlashToken */ || token === 61 /* SlashEqualsToken */) {
                var p = tokenPos + 1;
                var inEscape = false;
                var inCharacterClass = false;
                while (true) {
                    // If we reach the end of a file, or hit a newline, then this is an unterminated
                    // regex.  Report error and return what we have so far.
                    if (p >= end) {
                        tokenIsUnterminated = true;
                        error(ts.Diagnostics.Unterminated_regular_expression_literal);
                        break;
                    }
                    var ch = text.charCodeAt(p);
                    if (isLineBreak(ch)) {
                        tokenIsUnterminated = true;
                        error(ts.Diagnostics.Unterminated_regular_expression_literal);
                        break;
                    }
                    if (inEscape) {
                        // Parsing an escape character;
                        // reset the flag and just advance to the next char.
                        inEscape = false;
                    }
                    else if (ch === 47 /* slash */ && !inCharacterClass) {
                        // A slash within a character class is permissible,
                        // but in general it signals the end of the regexp literal.
                        p++;
                        break;
                    }
                    else if (ch === 91 /* openBracket */) {
                        inCharacterClass = true;
                    }
                    else if (ch === 92 /* backslash */) {
                        inEscape = true;
                    }
                    else if (ch === 93 /* closeBracket */) {
                        inCharacterClass = false;
                    }
                    p++;
                }
                while (p < end && isIdentifierPart(text.charCodeAt(p), languageVersion)) {
                    p++;
                }
                pos = p;
                tokenValue = text.substring(tokenPos, pos);
                token = 10 /* RegularExpressionLiteral */;
            }
            return token;
        }
        /**
         * Unconditionally back up and scan a template expression portion.
         */
        function reScanTemplateToken() {
            ts.Debug.assert(token === 16 /* CloseBraceToken */, "'reScanTemplateToken' should only be called on a '}'");
            pos = tokenPos;
            return token = scanTemplateAndSetTokenValue();
        }
        function reScanJsxToken() {
            pos = tokenPos = startPos;
            return token = scanJsxToken();
        }
        function scanJsxToken() {
            startPos = tokenPos = pos;
            if (pos >= end) {
                return token = 1 /* EndOfFileToken */;
            }
            var char = text.charCodeAt(pos);
            if (char === 60 /* lessThan */) {
                if (text.charCodeAt(pos + 1) === 47 /* slash */) {
                    pos += 2;
                    return token = 26 /* LessThanSlashToken */;
                }
                pos++;
                return token = 25 /* LessThanToken */;
            }
            if (char === 123 /* openBrace */) {
                pos++;
                return token = 15 /* OpenBraceToken */;
            }
            while (pos < end) {
                pos++;
                char = text.charCodeAt(pos);
                if ((char === 123 /* openBrace */) || (char === 60 /* lessThan */)) {
                    break;
                }
            }
            return token = 236 /* JsxText */;
        }
        // Scans a JSX identifier; these differ from normal identifiers in that
        // they allow dashes
        function scanJsxIdentifier() {
            if (tokenIsIdentifierOrKeyword(token)) {
                var firstCharPosition = pos;
                while (pos < end) {
                    var ch = text.charCodeAt(pos);
                    if (ch === 45 /* minus */ || ((firstCharPosition === pos) ? isIdentifierStart(ch, languageVersion) : isIdentifierPart(ch, languageVersion))) {
                        pos++;
                    }
                    else {
                        break;
                    }
                }
                tokenValue += text.substr(firstCharPosition, pos - firstCharPosition);
            }
            return token;
        }
        function speculationHelper(callback, isLookahead) {
            var savePos = pos;
            var saveStartPos = startPos;
            var saveTokenPos = tokenPos;
            var saveToken = token;
            var saveTokenValue = tokenValue;
            var savePrecedingLineBreak = precedingLineBreak;
            var result = callback();
            // If our callback returned something 'falsy' or we're just looking ahead,
            // then unconditionally restore us to where we were.
            if (!result || isLookahead) {
                pos = savePos;
                startPos = saveStartPos;
                tokenPos = saveTokenPos;
                token = saveToken;
                tokenValue = saveTokenValue;
                precedingLineBreak = savePrecedingLineBreak;
            }
            return result;
        }
        function lookAhead(callback) {
            return speculationHelper(callback, /*isLookahead:*/ true);
        }
        function tryScan(callback) {
            return speculationHelper(callback, /*isLookahead:*/ false);
        }
        function setText(newText, start, length) {
            text = newText || "";
            end = length === undefined ? text.length : start + length;
            setTextPos(start || 0);
        }
        function setOnError(errorCallback) {
            onError = errorCallback;
        }
        function setScriptTarget(scriptTarget) {
            languageVersion = scriptTarget;
        }
        function setLanguageVariant(variant) {
            languageVariant = variant;
        }
        function setTextPos(textPos) {
            ts.Debug.assert(textPos >= 0);
            pos = textPos;
            startPos = textPos;
            tokenPos = textPos;
            token = 0 /* Unknown */;
            precedingLineBreak = false;
            tokenValue = undefined;
            hasExtendedUnicodeEscape = false;
            tokenIsUnterminated = false;
        }
    }
function createScanner(languageVersion, skipTrivia, languageVariant, text, onError, start, length) {
        if (languageVariant === void 0) { languageVariant = 0 /* Standard */; }
        // Current position (end position of text of current token)
        var pos;
        // end of text
        var end;
        // Start position of whitespace before current token
        var startPos;
        // Start position of text of current token
        var tokenPos;
        var token;
        var tokenValue;
        var precedingLineBreak;
        var hasExtendedUnicodeEscape;
        var tokenIsUnterminated;
        setText(text, start, length);
        return {
            getStartPos: function () { return startPos; },
            getTextPos: function () { return pos; },
            getToken: function () { return token; },
            getTokenPos: function () { return tokenPos; },
            getTokenText: function () { return text.substring(tokenPos, pos); },
            getTokenValue: function () { return tokenValue; },
            hasExtendedUnicodeEscape: function () { return hasExtendedUnicodeEscape; },
            hasPrecedingLineBreak: function () { return precedingLineBreak; },
            isIdentifier: function () { return token === 69 /* Identifier */ || token > 105 /* LastReservedWord */; },
            isReservedWord: function () { return token >= 70 /* FirstReservedWord */ && token <= 105 /* LastReservedWord */; },
            isUnterminated: function () { return tokenIsUnterminated; },
            reScanGreaterToken: reScanGreaterToken,
            reScanSlashToken: reScanSlashToken,
            reScanTemplateToken: reScanTemplateToken,
            scanJsxIdentifier: scanJsxIdentifier,
            reScanJsxToken: reScanJsxToken,
            scanJsxToken: scanJsxToken,
            scan: scan,
            setText: setText,
            setScriptTarget: setScriptTarget,
            setLanguageVariant: setLanguageVariant,
            setOnError: setOnError,
            setTextPos: setTextPos,
            tryScan: tryScan,
            lookAhead: lookAhead
        };
        function error(message, length) {
            if (onError) {
                onError(message, length || 0);
            }
        }
        function scanNumber() {
            var start = pos;
            while (isDigit(text.charCodeAt(pos)))
                pos++;
            if (text.charCodeAt(pos) === 46 /* dot */) {
                pos++;
                while (isDigit(text.charCodeAt(pos)))
                    pos++;
            }
            var end = pos;
            if (text.charCodeAt(pos) === 69 /* E */ || text.charCodeAt(pos) === 101 /* e */) {
                pos++;
                if (text.charCodeAt(pos) === 43 /* plus */ || text.charCodeAt(pos) === 45 /* minus */)
                    pos++;
                if (isDigit(text.charCodeAt(pos))) {
                    pos++;
                    while (isDigit(text.charCodeAt(pos)))
                        pos++;
                    end = pos;
                }
                else {
                    error(ts.Diagnostics.Digit_expected);
                }
            }
            return +(text.substring(start, end));
        }
        function scanOctalDigits() {
            var start = pos;
            while (isOctalDigit(text.charCodeAt(pos))) {
                pos++;
            }
            return +(text.substring(start, pos));
        }
        /**
         * Scans the given number of hexadecimal digits in the text,
         * returning -1 if the given number is unavailable.
         */
        function scanExactNumberOfHexDigits(count) {
            return scanHexDigits(/*minCount*/ count, /*scanAsManyAsPossible*/ false);
        }
        /**
         * Scans as many hexadecimal digits as are available in the text,
         * returning -1 if the given number of digits was unavailable.
         */
        function scanMinimumNumberOfHexDigits(count) {
            return scanHexDigits(/*minCount*/ count, /*scanAsManyAsPossible*/ true);
        }
        function scanHexDigits(minCount, scanAsManyAsPossible) {
            var digits = 0;
            var value = 0;
            while (digits < minCount || scanAsManyAsPossible) {
                var ch = text.charCodeAt(pos);
                if (ch >= 48 /* _0 */ && ch <= 57 /* _9 */) {
                    value = value * 16 + ch - 48 /* _0 */;
                }
                else if (ch >= 65 /* A */ && ch <= 70 /* F */) {
                    value = value * 16 + ch - 65 /* A */ + 10;
                }
                else if (ch >= 97 /* a */ && ch <= 102 /* f */) {
                    value = value * 16 + ch - 97 /* a */ + 10;
                }
                else {
                    break;
                }
                pos++;
                digits++;
            }
            if (digits < minCount) {
                value = -1;
            }
            return value;
        }
        function scanString() {
            var quote = text.charCodeAt(pos++);
            var result = "";
            var start = pos;
            while (true) {
                if (pos >= end) {
                    result += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_string_literal);
                    break;
                }
                var ch = text.charCodeAt(pos);
                if (ch === quote) {
                    result += text.substring(start, pos);
                    pos++;
                    break;
                }
                if (ch === 92 /* backslash */) {
                    result += text.substring(start, pos);
                    result += scanEscapeSequence();
                    start = pos;
                    continue;
                }
                if (isLineBreak(ch)) {
                    result += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_string_literal);
                    break;
                }
                pos++;
            }
            return result;
        }
        /**
         * Sets the current 'tokenValue' and returns a NoSubstitutionTemplateLiteral or
         * a literal component of a TemplateExpression.
         */
        function scanTemplateAndSetTokenValue() {
            var startedWithBacktick = text.charCodeAt(pos) === 96 /* backtick */;
            pos++;
            var start = pos;
            var contents = "";
            var resultingToken;
            while (true) {
                if (pos >= end) {
                    contents += text.substring(start, pos);
                    tokenIsUnterminated = true;
                    error(ts.Diagnostics.Unterminated_template_literal);
                    resultingToken = startedWithBacktick ? 11 /* NoSubstitutionTemplateLiteral */ : 14 /* TemplateTail */;
                    break;
                }
                var currChar = text.charCodeAt(pos);
                // '`'
                if (currChar === 96 /* backtick */) {
                    contents += text.substring(start, pos);
                    pos++;
                    resultingToken = startedWithBacktick ? 11 /* NoSubstitutionTemplateLiteral */ : 14 /* TemplateTail */;
                    break;
                }
                // '${'
                if (currChar === 36 /* $ */ && pos + 1 < end && text.charCodeAt(pos + 1) === 123 /* openBrace */) {
                    contents += text.substring(start, pos);
                    pos += 2;
                    resultingToken = startedWithBacktick ? 12 /* TemplateHead */ : 13 /* TemplateMiddle */;
                    break;
                }
                // Escape character
                if (currChar === 92 /* backslash */) {
                    contents += text.substring(start, pos);
                    contents += scanEscapeSequence();
                    start = pos;
                    continue;
                }
                // Speculated ECMAScript 6 Spec 11.8.6.1:
                // <CR><LF> and <CR> LineTerminatorSequences are normalized to <LF> for Template Values
                if (currChar === 13 /* carriageReturn */) {
                    contents += text.substring(start, pos);
                    pos++;
                    if (pos < end && text.charCodeAt(pos) === 10 /* lineFeed */) {
                        pos++;
                    }
                    contents += "\n";
                    start = pos;
                    continue;
                }
                pos++;
            }
            ts.Debug.assert(resultingToken !== undefined);
            tokenValue = contents;
            return resultingToken;
        }
        function scanEscapeSequence() {
            pos++;
            if (pos >= end) {
                error(ts.Diagnostics.Unexpected_end_of_text);
                return "";
            }
            var ch = text.charCodeAt(pos++);
            switch (ch) {
                case 48 /* _0 */:
                    return "\0";
                case 98 /* b */:
                    return "\b";
                case 116 /* t */:
                    return "\t";
                case 110 /* n */:
                    return "\n";
                case 118 /* v */:
                    return "\v";
                case 102 /* f */:
                    return "\f";
                case 114 /* r */:
                    return "\r";
                case 39 /* singleQuote */:
                    return "\'";
                case 34 /* doubleQuote */:
                    return "\"";
                case 117 /* u */:
                    // '\u{DDDDDDDD}'
                    if (pos < end && text.charCodeAt(pos) === 123 /* openBrace */) {
                        hasExtendedUnicodeEscape = true;
                        pos++;
                        return scanExtendedUnicodeEscape();
                    }
                    // '\uDDDD'
                    return scanHexadecimalEscape(/*numDigits*/ 4);
                case 120 /* x */:
                    // '\xDD'
                    return scanHexadecimalEscape(/*numDigits*/ 2);
                // when encountering a LineContinuation (i.e. a backslash and a line terminator sequence),
                // the line terminator is interpreted to be "the empty code unit sequence".
                case 13 /* carriageReturn */:
                    if (pos < end && text.charCodeAt(pos) === 10 /* lineFeed */) {
                        pos++;
                    }
                // fall through
                case 10 /* lineFeed */:
                case 8232 /* lineSeparator */:
                case 8233 /* paragraphSeparator */:
                    return "";
                default:
                    return String.fromCharCode(ch);
            }
        }
        function scanHexadecimalEscape(numDigits) {
            var escapedValue = scanExactNumberOfHexDigits(numDigits);
            if (escapedValue >= 0) {
                return String.fromCharCode(escapedValue);
            }
            else {
                error(ts.Diagnostics.Hexadecimal_digit_expected);
                return "";
            }
        }
        function scanExtendedUnicodeEscape() {
            var escapedValue = scanMinimumNumberOfHexDigits(1);
            var isInvalidExtendedEscape = false;
            // Validate the value of the digit
            if (escapedValue < 0) {
                error(ts.Diagnostics.Hexadecimal_digit_expected);
                isInvalidExtendedEscape = true;
            }
            else if (escapedValue > 0x10FFFF) {
                error(ts.Diagnostics.An_extended_Unicode_escape_value_must_be_between_0x0_and_0x10FFFF_inclusive);
                isInvalidExtendedEscape = true;
            }
            if (pos >= end) {
                error(ts.Diagnostics.Unexpected_end_of_text);
                isInvalidExtendedEscape = true;
            }
            else if (text.charCodeAt(pos) === 125 /* closeBrace */) {
                // Only swallow the following character up if it's a '}'.
                pos++;
            }
            else {
                error(ts.Diagnostics.Unterminated_Unicode_escape_sequence);
                isInvalidExtendedEscape = true;
            }
            if (isInvalidExtendedEscape) {
                return "";
            }
            return utf16EncodeAsString(escapedValue);
        }
        // Derived from the 10.1.1 UTF16Encoding of the ES6 Spec.
        function utf16EncodeAsString(codePoint) {
            ts.Debug.assert(0x0 <= codePoint && codePoint <= 0x10FFFF);
            if (codePoint <= 65535) {
                return String.fromCharCode(codePoint);
            }
            var codeUnit1 = Math.floor((codePoint - 65536) / 1024) + 0xD800;
            var codeUnit2 = ((codePoint - 65536) % 1024) + 0xDC00;
            return String.fromCharCode(codeUnit1, codeUnit2);
        }
        // Current character is known to be a backslash. Check for Unicode escape of the form '\uXXXX'
        // and return code point value if valid Unicode escape is found. Otherwise return -1.
        function peekUnicodeEscape() {
            if (pos + 5 < end && text.charCodeAt(pos + 1) === 117 /* u */) {
                var start_1 = pos;
                pos += 2;
                var value = scanExactNumberOfHexDigits(4);
                pos = start_1;
                return value;
            }
            return -1;
        }
        function scanIdentifierParts() {
            var result = "";
            var start = pos;
            while (pos < end) {
                var ch = text.charCodeAt(pos);
                if (isIdentifierPart(ch, languageVersion)) {
                    pos++;
                }
                else if (ch === 92 /* backslash */) {
                    ch = peekUnicodeEscape();
                    if (!(ch >= 0 && isIdentifierPart(ch, languageVersion))) {
                        break;
                    }
                    result += text.substring(start, pos);
                    result += String.fromCharCode(ch);
                    // Valid Unicode escape is always six characters
                    pos += 6;
                    start = pos;
                }
                else {
                    break;
                }
            }
            result += text.substring(start, pos);
            return result;
        }
        function getIdentifierToken() {
            // Reserved words are between 2 and 11 characters long and start with a lowercase letter
            var len = tokenValue.length;
            if (len >= 2 && len <= 11) {
                var ch = tokenValue.charCodeAt(0);
                if (ch >= 97 /* a */ && ch <= 122 /* z */ && hasOwnProperty.call(textToToken, tokenValue)) {
                    return token = textToToken[tokenValue];
                }
            }
            return token = 69 /* Identifier */;
        }
        function scanBinaryOrOctalDigits(base) {
            ts.Debug.assert(base !== 2 || base !== 8, "Expected either base 2 or base 8");
            var value = 0;
            // For counting number of digits; Valid binaryIntegerLiteral must have at least one binary digit following B or b.
            // Similarly valid octalIntegerLiteral must have at least one octal digit following o or O.
            var numberOfDigits = 0;
            while (true) {
                var ch = text.charCodeAt(pos);
                var valueOfCh = ch - 48 /* _0 */;
                if (!isDigit(ch) || valueOfCh >= base) {
                    break;
                }
                value = value * base + valueOfCh;
                pos++;
                numberOfDigits++;
            }
            // Invalid binaryIntegerLiteral or octalIntegerLiteral
            if (numberOfDigits === 0) {
                return -1;
            }
            return value;
        }
        function scan() {
            startPos = pos;
            hasExtendedUnicodeEscape = false;
            precedingLineBreak = false;
            tokenIsUnterminated = false;
            while (true) {
                tokenPos = pos;
                if (pos >= end) {
                    return token = 1 /* EndOfFileToken */;
                }
                var ch = text.charCodeAt(pos);
                // Special handling for shebang
                if (ch === 35 /* hash */ && pos === 0 && isShebangTrivia(text, pos)) {
                    pos = scanShebangTrivia(text, pos);
                    if (skipTrivia) {
                        continue;
                    }
                    else {
                        return token = 6 /* ShebangTrivia */;
                    }
                }
                switch (ch) {
                    case 10 /* lineFeed */:
                    case 13 /* carriageReturn */:
                        precedingLineBreak = true;
                        if (skipTrivia) {
                            pos++;
                            continue;
                        }
                        else {
                            if (ch === 13 /* carriageReturn */ && pos + 1 < end && text.charCodeAt(pos + 1) === 10 /* lineFeed */) {
                                // consume both CR and LF
                                pos += 2;
                            }
                            else {
                                pos++;
                            }
                            return token = 4 /* NewLineTrivia */;
                        }
                    case 9 /* tab */:
                    case 11 /* verticalTab */:
                    case 12 /* formFeed */:
                    case 32 /* space */:
                        if (skipTrivia) {
                            pos++;
                            continue;
                        }
                        else {
                            while (pos < end && isWhiteSpace(text.charCodeAt(pos))) {
                                pos++;
                            }
                            return token = 5 /* WhitespaceTrivia */;
                        }
                    case 33 /* exclamation */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 33 /* ExclamationEqualsEqualsToken */;
                            }
                            return pos += 2, token = 31 /* ExclamationEqualsToken */;
                        }
                        return pos++, token = 49 /* ExclamationToken */;
                    case 34 /* doubleQuote */:
                    case 39 /* singleQuote */:
                        tokenValue = scanString();
                        return token = 9 /* StringLiteral */;
                    case 96 /* backtick */:
                        return token = scanTemplateAndSetTokenValue();
                    case 37 /* percent */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 62 /* PercentEqualsToken */;
                        }
                        return pos++, token = 40 /* PercentToken */;
                    case 38 /* ampersand */:
                        if (text.charCodeAt(pos + 1) === 38 /* ampersand */) {
                            return pos += 2, token = 51 /* AmpersandAmpersandToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 66 /* AmpersandEqualsToken */;
                        }
                        return pos++, token = 46 /* AmpersandToken */;
                    case 40 /* openParen */:
                        return pos++, token = 17 /* OpenParenToken */;
                    case 41 /* closeParen */:
                        return pos++, token = 18 /* CloseParenToken */;
                    case 42 /* asterisk */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 59 /* AsteriskEqualsToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 42 /* asterisk */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 60 /* AsteriskAsteriskEqualsToken */;
                            }
                            return pos += 2, token = 38 /* AsteriskAsteriskToken */;
                        }
                        return pos++, token = 37 /* AsteriskToken */;
                    case 43 /* plus */:
                        if (text.charCodeAt(pos + 1) === 43 /* plus */) {
                            return pos += 2, token = 41 /* PlusPlusToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 57 /* PlusEqualsToken */;
                        }
                        return pos++, token = 35 /* PlusToken */;
                    case 44 /* comma */:
                        return pos++, token = 24 /* CommaToken */;
                    case 45 /* minus */:
                        if (text.charCodeAt(pos + 1) === 45 /* minus */) {
                            return pos += 2, token = 42 /* MinusMinusToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 58 /* MinusEqualsToken */;
                        }
                        return pos++, token = 36 /* MinusToken */;
                    case 46 /* dot */:
                        if (isDigit(text.charCodeAt(pos + 1))) {
                            tokenValue = "" + scanNumber();
                            return token = 8 /* NumericLiteral */;
                        }
                        if (text.charCodeAt(pos + 1) === 46 /* dot */ && text.charCodeAt(pos + 2) === 46 /* dot */) {
                            return pos += 3, token = 22 /* DotDotDotToken */;
                        }
                        return pos++, token = 21 /* DotToken */;
                    case 47 /* slash */:
                        // Single-line comment
                        if (text.charCodeAt(pos + 1) === 47 /* slash */) {
                            pos += 2;
                            while (pos < end) {
                                if (isLineBreak(text.charCodeAt(pos))) {
                                    break;
                                }
                                pos++;
                            }
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 2 /* SingleLineCommentTrivia */;
                            }
                        }
                        // Multi-line comment
                        if (text.charCodeAt(pos + 1) === 42 /* asterisk */) {
                            pos += 2;
                            var commentClosed = false;
                            while (pos < end) {
                                var ch_2 = text.charCodeAt(pos);
                                if (ch_2 === 42 /* asterisk */ && text.charCodeAt(pos + 1) === 47 /* slash */) {
                                    pos += 2;
                                    commentClosed = true;
                                    break;
                                }
                                if (isLineBreak(ch_2)) {
                                    precedingLineBreak = true;
                                }
                                pos++;
                            }
                            if (!commentClosed) {
                                error(ts.Diagnostics.Asterisk_Slash_expected);
                            }
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                tokenIsUnterminated = !commentClosed;
                                return token = 3 /* MultiLineCommentTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 61 /* SlashEqualsToken */;
                        }
                        return pos++, token = 39 /* SlashToken */;
                    case 48 /* _0 */:
                        if (pos + 2 < end && (text.charCodeAt(pos + 1) === 88 /* X */ || text.charCodeAt(pos + 1) === 120 /* x */)) {
                            pos += 2;
                            var value = scanMinimumNumberOfHexDigits(1);
                            if (value < 0) {
                                error(ts.Diagnostics.Hexadecimal_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        else if (pos + 2 < end && (text.charCodeAt(pos + 1) === 66 /* B */ || text.charCodeAt(pos + 1) === 98 /* b */)) {
                            pos += 2;
                            var value = scanBinaryOrOctalDigits(/* base */ 2);
                            if (value < 0) {
                                error(ts.Diagnostics.Binary_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        else if (pos + 2 < end && (text.charCodeAt(pos + 1) === 79 /* O */ || text.charCodeAt(pos + 1) === 111 /* o */)) {
                            pos += 2;
                            var value = scanBinaryOrOctalDigits(/* base */ 8);
                            if (value < 0) {
                                error(ts.Diagnostics.Octal_digit_expected);
                                value = 0;
                            }
                            tokenValue = "" + value;
                            return token = 8 /* NumericLiteral */;
                        }
                        // Try to parse as an octal
                        if (pos + 1 < end && isOctalDigit(text.charCodeAt(pos + 1))) {
                            tokenValue = "" + scanOctalDigits();
                            return token = 8 /* NumericLiteral */;
                        }
                    // This fall-through is a deviation from the EcmaScript grammar. The grammar says that a leading zero
                    // can only be followed by an octal digit, a dot, or the end of the number literal. However, we are being
                    // permissive and allowing decimal digits of the form 08* and 09* (which many browsers also do).
                    case 49 /* _1 */:
                    case 50 /* _2 */:
                    case 51 /* _3 */:
                    case 52 /* _4 */:
                    case 53 /* _5 */:
                    case 54 /* _6 */:
                    case 55 /* _7 */:
                    case 56 /* _8 */:
                    case 57 /* _9 */:
                        tokenValue = "" + scanNumber();
                        return token = 8 /* NumericLiteral */;
                    case 58 /* colon */:
                        return pos++, token = 54 /* ColonToken */;
                    case 59 /* semicolon */:
                        return pos++, token = 23 /* SemicolonToken */;
                    case 60 /* lessThan */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 60 /* lessThan */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 63 /* LessThanLessThanEqualsToken */;
                            }
                            return pos += 2, token = 43 /* LessThanLessThanToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 28 /* LessThanEqualsToken */;
                        }
                        if (languageVariant === 1 /* JSX */ &&
                            text.charCodeAt(pos + 1) === 47 /* slash */ &&
                            text.charCodeAt(pos + 2) !== 42 /* asterisk */) {
                            return pos += 2, token = 26 /* LessThanSlashToken */;
                        }
                        return pos++, token = 25 /* LessThanToken */;
                    case 61 /* equals */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                                return pos += 3, token = 32 /* EqualsEqualsEqualsToken */;
                            }
                            return pos += 2, token = 30 /* EqualsEqualsToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 62 /* greaterThan */) {
                            return pos += 2, token = 34 /* EqualsGreaterThanToken */;
                        }
                        return pos++, token = 56 /* EqualsToken */;
                    case 62 /* greaterThan */:
                        if (isConflictMarkerTrivia(text, pos)) {
                            pos = scanConflictMarkerTrivia(text, pos, error);
                            if (skipTrivia) {
                                continue;
                            }
                            else {
                                return token = 7 /* ConflictMarkerTrivia */;
                            }
                        }
                        return pos++, token = 27 /* GreaterThanToken */;
                    case 63 /* question */:
                        return pos++, token = 53 /* QuestionToken */;
                    case 91 /* openBracket */:
                        return pos++, token = 19 /* OpenBracketToken */;
                    case 93 /* closeBracket */:
                        return pos++, token = 20 /* CloseBracketToken */;
                    case 94 /* caret */:
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 68 /* CaretEqualsToken */;
                        }
                        return pos++, token = 48 /* CaretToken */;
                    case 123 /* openBrace */:
                        return pos++, token = 15 /* OpenBraceToken */;
                    case 124 /* bar */:
                        if (text.charCodeAt(pos + 1) === 124 /* bar */) {
                            return pos += 2, token = 52 /* BarBarToken */;
                        }
                        if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                            return pos += 2, token = 67 /* BarEqualsToken */;
                        }
                        return pos++, token = 47 /* BarToken */;
                    case 125 /* closeBrace */:
                        return pos++, token = 16 /* CloseBraceToken */;
                    case 126 /* tilde */:
                        return pos++, token = 50 /* TildeToken */;
                    case 64 /* at */:
                        return pos++, token = 55 /* AtToken */;
                    case 92 /* backslash */:
                        var cookedChar = peekUnicodeEscape();
                        if (cookedChar >= 0 && isIdentifierStart(cookedChar, languageVersion)) {
                            pos += 6;
                            tokenValue = String.fromCharCode(cookedChar) + scanIdentifierParts();
                            return token = getIdentifierToken();
                        }
                        error(ts.Diagnostics.Invalid_character);
                        return pos++, token = 0 /* Unknown */;
                    default:
                        if (isIdentifierStart(ch, languageVersion)) {
                            pos++;
                            while (pos < end && isIdentifierPart(ch = text.charCodeAt(pos), languageVersion))
                                pos++;
                            tokenValue = text.substring(tokenPos, pos);
                            if (ch === 92 /* backslash */) {
                                tokenValue += scanIdentifierParts();
                            }
                            return token = getIdentifierToken();
                        }
                        else if (isWhiteSpace(ch)) {
                            pos++;
                            continue;
                        }
                        else if (isLineBreak(ch)) {
                            precedingLineBreak = true;
                            pos++;
                            continue;
                        }
                        error(ts.Diagnostics.Invalid_character);
                        return pos++, token = 0 /* Unknown */;
                }
            }
        }
        function reScanGreaterToken() {
            if (token === 27 /* GreaterThanToken */) {
                if (text.charCodeAt(pos) === 62 /* greaterThan */) {
                    if (text.charCodeAt(pos + 1) === 62 /* greaterThan */) {
                        if (text.charCodeAt(pos + 2) === 61 /* equals */) {
                            return pos += 3, token = 65 /* GreaterThanGreaterThanGreaterThanEqualsToken */;
                        }
                        return pos += 2, token = 45 /* GreaterThanGreaterThanGreaterThanToken */;
                    }
                    if (text.charCodeAt(pos + 1) === 61 /* equals */) {
                        return pos += 2, token = 64 /* GreaterThanGreaterThanEqualsToken */;
                    }
                    return pos++, token = 44 /* GreaterThanGreaterThanToken */;
                }
                if (text.charCodeAt(pos) === 61 /* equals */) {
                    return pos++, token = 29 /* GreaterThanEqualsToken */;
                }
            }
            return token;
        }
        function reScanSlashToken() {
            if (token === 39 /* SlashToken */ || token === 61 /* SlashEqualsToken */) {
                var p = tokenPos + 1;
                var inEscape = false;
                var inCharacterClass = false;
                while (true) {
                    // If we reach the end of a file, or hit a newline, then this is an unterminated
                    // regex.  Report error and return what we have so far.
                    if (p >= end) {
                        tokenIsUnterminated = true;
                        error(ts.Diagnostics.Unterminated_regular_expression_literal);
                        break;
                    }
                    var ch = text.charCodeAt(p);
                    if (isLineBreak(ch)) {
                        tokenIsUnterminated = true;
                        error(ts.Diagnostics.Unterminated_regular_expression_literal);
                        break;
                    }
                    if (inEscape) {
                        // Parsing an escape character;
                        // reset the flag and just advance to the next char.
                        inEscape = false;
                    }
                    else if (ch === 47 /* slash */ && !inCharacterClass) {
                        // A slash within a character class is permissible,
                        // but in general it signals the end of the regexp literal.
                        p++;
                        break;
                    }
                    else if (ch === 91 /* openBracket */) {
                        inCharacterClass = true;
                    }
                    else if (ch === 92 /* backslash */) {
                        inEscape = true;
                    }
                    else if (ch === 93 /* closeBracket */) {
                        inCharacterClass = false;
                    }
                    p++;
                }
                while (p < end && isIdentifierPart(text.charCodeAt(p), languageVersion)) {
                    p++;
                }
                pos = p;
                tokenValue = text.substring(tokenPos, pos);
                token = 10 /* RegularExpressionLiteral */;
            }
            return token;
        }
        /**
         * Unconditionally back up and scan a template expression portion.
         */
        function reScanTemplateToken() {
            ts.Debug.assert(token === 16 /* CloseBraceToken */, "'reScanTemplateToken' should only be called on a '}'");
            pos = tokenPos;
            return token = scanTemplateAndSetTokenValue();
        }
        function reScanJsxToken() {
            pos = tokenPos = startPos;
            return token = scanJsxToken();
        }
        function scanJsxToken() {
            startPos = tokenPos = pos;
            if (pos >= end) {
                return token = 1 /* EndOfFileToken */;
            }
            var char = text.charCodeAt(pos);
            if (char === 60 /* lessThan */) {
                if (text.charCodeAt(pos + 1) === 47 /* slash */) {
                    pos += 2;
                    return token = 26 /* LessThanSlashToken */;
                }
                pos++;
                return token = 25 /* LessThanToken */;
            }
            if (char === 123 /* openBrace */) {
                pos++;
                return token = 15 /* OpenBraceToken */;
            }
            while (pos < end) {
                pos++;
                char = text.charCodeAt(pos);
                if ((char === 123 /* openBrace */) || (char === 60 /* lessThan */)) {
                    break;
                }
            }
            return token = 236 /* JsxText */;
        }
        // Scans a JSX identifier; these differ from normal identifiers in that
        // they allow dashes
        function scanJsxIdentifier() {
            if (tokenIsIdentifierOrKeyword(token)) {
                var firstCharPosition = pos;
                while (pos < end) {
                    var ch = text.charCodeAt(pos);
                    if (ch === 45 /* minus */ || ((firstCharPosition === pos) ? isIdentifierStart(ch, languageVersion) : isIdentifierPart(ch, languageVersion))) {
                        pos++;
                    }
                    else {
                        break;
                    }
                }
                tokenValue += text.substr(firstCharPosition, pos - firstCharPosition);
            }
            return token;
        }
        function speculationHelper(callback, isLookahead) {
            var savePos = pos;
            var saveStartPos = startPos;
            var saveTokenPos = tokenPos;
            var saveToken = token;
            var saveTokenValue = tokenValue;
            var savePrecedingLineBreak = precedingLineBreak;
            var result = callback();
            // If our callback returned something 'falsy' or we're just looking ahead,
            // then unconditionally restore us to where we were.
            if (!result || isLookahead) {
                pos = savePos;
                startPos = saveStartPos;
                tokenPos = saveTokenPos;
                token = saveToken;
                tokenValue = saveTokenValue;
                precedingLineBreak = savePrecedingLineBreak;
            }
            return result;
        }
        function lookAhead(callback) {
            return speculationHelper(callback, /*isLookahead:*/ true);
        }
        function tryScan(callback) {
            return speculationHelper(callback, /*isLookahead:*/ false);
        }
        function setText(newText, start, length) {
            text = newText || "";
            end = length === undefined ? text.length : start + length;
            setTextPos(start || 0);
        }
        function setOnError(errorCallback) {
            onError = errorCallback;
        }
        function setScriptTarget(scriptTarget) {
            languageVersion = scriptTarget;
        }
        function setLanguageVariant(variant) {
            languageVariant = variant;
        }
        function setTextPos(textPos) {
            ts.Debug.assert(textPos >= 0);
            pos = textPos;
            startPos = textPos;
            tokenPos = textPos;
            token = 0 /* Unknown */;
            precedingLineBreak = false;
            tokenValue = undefined;
            hasExtendedUnicodeEscape = false;
            tokenIsUnterminated = false;
        }
    }
Creates a scanner over a (possibly unspecified) range of a piece of text.