angular 1 pass promise to directive w/out isolate scope

index.html

<div ng-app="app" ng-controller="Controller as vm" directive="directive" promise="vm.promise"></div>

script.js

angular
  .module('app', [])
  .controller('Controller', ['$q', Controller])
  .directive('directive', directive)

function Controller($q) {
  this.promise = () => $q.when().then(() => console.log('!'))
}

function directive() {
  return (scope, _, attrs) => {
    const promise = scope.$eval(attrs.promise)
    promise().then(() => console.log('?'))
  }
}