title: Angular: Token error when expression passed to custom directive with isolated scope
body: <p>(messages, code, etc, is a bit modified to explain issue)</p>
  
  <p>The error: </p>
  
  <pre><code>Syntax Error: Token 'promiseObject' is unexpected, expecting [:] at column 3 of the expression [{{promiseObject?promiseObject.activeDEM:0}}] starting at [promiseObject?promiseObject.activeDEM:0}}].
  </code></pre>
  
  <p>Following code explains the issue: </p>
  
  <p>HTML used:</p>
  
  <pre><code>&lt;count-up id="feafdcds" duration="1" end-val='{{promiseObject?promiseObject.value:0}}' class="number" &gt;&lt;/count-up&gt;
  </code></pre>
  
  <p>The directive used has an isolated scope. if isolated scope is removed, the error goes away, BUT, then I don't know how to watch my attributes for change.</p>
  
  <pre><code>angular.module('core-metronic').directive('countUp', ['$filter',
      function ($filter) {
  
          return {
              restrict: 'E',
              scope: {
                  endVal: '='
              },
              link: function ($scope, $el, $attrs) {
                  $scope.$watch('endVal',function(newValue,oldValue)
                  {
                      if(newValue)
                          alert(newValue); 
                  },true);
  
                  //...more code...
  
              }
  
          }
      }
  ]);
  </code></pre>