Write http interceptor as class

I'm having trouble writing an angular http interceptor in plain TypeScript. The code I'm trying to convert is the following:

.config(['$httpProvider', function ($httpProvider) {

    var interceptor = ['$rootScope', '$q', 'httpBuffer', function ($rootScope, $q, httpBuffer) {
        function success(response) {
            return response;
        }

        function error(response) {
            if (response.status === 401 && !response.config.ignoreAuthModule) {
                var deferred = $q.defer();
                httpBuffer.append(response.config, deferred);
                $rootScope.$broadcast('event:auth-loginRequired', response);
                return deferred.promise;
            }
            // otherwise, default behaviour
            return $q.reject(response);
        }

        return function (promise) {
            return promise.then(success, error);
        };

    }];
    $httpProvider.responseInterceptors.push(interceptor);
}])

The first parts are clear, write a class with a constructor that takes the three dependencies $rootScope, $q and httpBuffer. Also write two private methods success and response.

class MyInterceptorClass {
    constructor(private $rootScope: ng.IRootScopeService, private $q: ng.IQService, private httpBuffer: HttpBuffer) {
    }

    private success(response: ng.IHttpPromiseCallbackArg<any>): ng.IHttpPromiseCallbackArg<any> {
        return response;
    }

    private error(response: ng.IHttpPromiseCallbackArg<any>): ng.IHttpPromiseCallbackArg<any> {
        if (response.status == 401 && !((<any>response.config).ignoreAuthModule)) {
            var deferred = this.$q.defer();
            this.httpBuffer.append(response.config, deferred);
            this.$rootScope.$broadcast('event:auth-loginRequired', response);

            return deferred.promise;
        }

        // Otherwise, default behavior
        return this.$q.reject(response);
    }
}

Also the registration of the interceptor should be clear:

.config(['$httpProvider', ($httpProvider: ng.IHttpProvider)=> {
    $httpProvider.responseInterceptors.push(['$rootScope', '$q', 'httpBuffer', MyInterceptorClass]);
}]);

What I am having trouble with is the last part of the original JavaScript, the return value of an anonymous function. How would I create this in TypeScript? As far as I understood this would be a nameless method in TypeScript, but this is not possible.