docs: 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
          };
      }