Angularjs：属性中缺少括号

“错误：[$parse：syntax]语法错误：从[{asset.sn}}开始的表达式[{{asset.sn}}]的第2列处的令牌'{‘无效键].
http://errors.angularjs.org/1.3.11/ $parse / syntax？p0 = {& p1 =无效密钥& p2 = 2& p3 = {{asset.sn}}& p4 = {asset.sn}}
minErr /< @ http://localhost:8000/app/vendor/angular/angular.js:63:12

这意味着什么以及为什么它显而易见？

HTML代码：

<table class="table" ng-table="tableParams" show-filter="false" ng-class="{loadingtable : loading}" ng-show="showResults">
                <tbody>
                    <tr ng-repeat="asset in assets">
                        <td class="col-md-4" data-title="'Serial Number'" header-class="text-left" search-word-marker param="{{asset.sn}}"></td>
                        <td class="col-md-4" data-title="'Asset Name'" accesskey="" header-class="text-left" search-word-marker param="{{asset.asset_name}}"></td>
                        <td class="col-md-2" data-title="'Asset Type'" header-class="text-left">{{asset.asset_type}}</td>
                        <td class="col-md-2" data-title="'Tags'" header-class="text-left">{{asset.tags}}</td>
                        <td class="col-md-1">
                            <div class="btn-group">
                                <span>
                                    <button type="button" class="btn btn-sm btn-primary" ng-click="viewAsset(asset.sn);">{{'VIEW' | translate}}</button>
                                </span>
                            </div>
                        </td>
                    </tr>
                </tbody>
            </table>

指令代码：

Application.Directives.directive('searchWordMarker',['$log','$rootScope',function ($log,$rootScope) {
    return {
        restrict: 'A',scope: {
            param: '='
        },//template: "{{myNewString}}",//replace: false,link: function (scope,el,attr) {

            var myString = attr.param;

            var searchWord = $rootScope.searchWord;

            var regex = new RegExp(searchWord,"g");
            var myNewString = myString.replace(regex,"<B>" + searchWord + "</B>");


            el[0].innerHTML = myNewString;


        }
    }
}]);