Javascript 获取ngRepeat错误（错误：ngRepeat:iidexp无效标识符）

控制器代码：

function usersView() {
    var directive = {
        templateUrl      : "users/users.html",
        restrict         : "E",
        replace          : true,
        bindToController : true,
        controller       : UsersCtrl,
        controllerAs     : 'usrs',
        link             : link,
        scope            : {}
    };
    return directive;
    function link(scope, element, attrs) {}
}

//....

initUsersDirect();

function initUsersDirect() {
    ApiFactory.getUsers().success(function(data) {
        vm.usersList = data.users;
        displayUsersList();
        console.log('vm.usersList',vm.usersList);
    });
}

function displayUsersList() {
    vm.usersLoaded = true;
}

这是usersList中的1个用户对象的外观：

{
    active: 1
    firstname: "Alexander"
    id: 1345324526
    lastname: "Finkle"
    role_id: 4
    session: Object
    username: "stackoverflow@gmail.com"
}

标记：

<tbody>
    <tr ng-repeat="{ u in usrs.usersList track by u.id }">
        <td class="td-name">{ u.firstname } { u.lastname }</td>
        <td class="sort-email">{ u.username }</td>
        <td class="sort-login">{ u.session.formatted_date }</td>
        <td class="sort-role">{ u.role_id }</td>
        <td><button class="btn-green-sm">Remove</button></td>
    </tr>
    <tr>
        <td>{{usrs.usersList}}</td>
    </tr>
</tbody>

{u.firstname}{u.lastname}
{u.username}
{u.session.formatted_date}
{u.role_id}
去除
{{usrs.usersList}

知道我为什么会犯这个错误吗

标记应为：

<tbody>
    <tr ng-repeat="u in usrs.usersList track by u.id">
        <td class="td-name">{{ u.firstname }} {{ u.lastname }}</td>
        <td class="sort-email">{{ u.username }}</td>
        <td class="sort-login">{{ u.session.formatted_date }}</td>
        <td class="sort-role">{{ u.role_id }}</td>
        <td><button class="btn-green-sm">Remove</button></td>
    </tr>
    <tr>
        <td>{{usrs.usersList}}</td>
    </tr>
</tbody>

{{u.firstname}{{u.lastname}}
{{u.username}
{{u.session.formatted_date}
{{u.role_id}
去除
{{usrs.usersList}

标记应为：

<tbody>
    <tr ng-repeat="u in usrs.usersList track by u.id">
        <td class="td-name">{{ u.firstname }} {{ u.lastname }}</td>
        <td class="sort-email">{{ u.username }}</td>
        <td class="sort-login">{{ u.session.formatted_date }}</td>
        <td class="sort-role">{{ u.role_id }}</td>
        <td><button class="btn-green-sm">Remove</button></td>
    </tr>
    <tr>
        <td>{{usrs.usersList}}</td>
    </tr>
</tbody>

{{u.firstname}{{u.lastname}}
{{u.username}
{{u.session.formatted_date}
{{u.role_id}
去除
{{usrs.usersList}