Quiero usar el atributo ng-model en un elemento personalizado. El problema es que necesito configurar el modelo ng con una expresión:

ng-model="{{anyVariable}}"

El problema es que siempre recibo un error tan pronto como agrego la expresión al atributo ng-model en mi plantilla:

Error: Syntax Error: Token 'x.name' is unexpected, expecting [:] at column 3 of the expression [{{x.name}}] starting at [x.name}}].
    at Error (<anonymous>)
    at throwError (http://localhost:9000/public/javascripts/angular.js:5999:11)
    at consume (http://localhost:9000/public/javascripts/angular.js:6037:7)
    at object (http://localhost:9000/public/javascripts/angular.js:6327:9)
    at primary (http://localhost:9000/public/javascripts/angular.js:6211:17)
    at unary (http://localhost:9000/public/javascripts/angular.js:6198:14)
    at multiplicative (http://localhost:9000/public/javascripts/angular.js:6181:16)
    at additive (http://localhost:9000/public/javascripts/angular.js:6172:16)
    at relational (http://localhost:9000/public/javascripts/angular.js:6163:16)
    at equality (http://localhost:9000/public/javascripts/angular.js:6154:16) 

El código utilizado:

function addFormFieldDirective(elementName, template) {
    app.directive(elementName, function() {
        return {
            restrict: "E",
            scope: {},
            replace: true,
                              // adds some extra layout
            template: buildFormTemplate(template),
            link: function(scope, elm, attrs) {
                scope.x = attrs;
            }
         };
    });
}
addFormFieldDirective("textfield", '<input id="{{x.id}}" ng-model="{{x.name}}" type="text" name="{{x.name}}" value="{{x.value}}" />');