Ember.assign polyfill uses Object.assign directly

packages/@ember/-internals/routing/lib/system/router.ts

@@ -9,7 +9,6 @@ import Controller from '@ember/controller';
 import { assert, deprecate, info } from '@ember/debug';
 import { APP_CTRL_ROUTER_PROPS, ROUTER_EVENTS } from '@ember/deprecated-features';
 import EmberError from '@ember/error';
-import { assign } from '@ember/polyfills';
 import { cancel, once, run, scheduleOnce } from '@ember/runloop';
 import { DEBUG } from '@glimmer/env';
 import EmberLocation, { EmberLocation as IEmberLocation } from '../location/api';
@@ -1018,7 +1017,7 @@ class EmberRouter extends EmberObject.extend(Evented) implements Evented {
 
     this._processActiveTransitionQueryParams(targetRouteName, models, queryParams, _queryParams);
 
-    assign(queryParams, _queryParams);
+    Object.assign(queryParams, _queryParams);
     this._prepareQueryParams(
       targetRouteName,
       models,
@@ -1059,7 +1058,7 @@ class EmberRouter extends EmberObject.extend(Evented) implements Evented {
     // from the active transition.
     this._fullyScopeQueryParams(targetRouteName, models, _queryParams);
     this._fullyScopeQueryParams(targetRouteName, models, unchangedQPs);
-    assign(queryParams, unchangedQPs);
+    Object.assign(queryParams, unchangedQPs);
   }
 
   /**
@@ -1156,7 +1155,7 @@ class EmberRouter extends EmberObject.extend(Evented) implements Evented {
         qps.push(qp);
       }
 
-      assign(map, qpMeta.map);
+      Object.assign(map, qpMeta.map);
     }
 
     let finalQPMeta = { qps, map };

packages/@ember/deprecated-features/index.ts

@@ -8,4 +8,4 @@ export const JQUERY_INTEGRATION = !!'3.9.0';
 export const APP_CTRL_ROUTER_PROPS = !!'3.10.0-beta.1';
 export const MOUSE_ENTER_LEAVE_MOVE_EVENTS = !!'3.13.0-beta.1';
 export const PARTIALS = !!'3.15.0-beta.1';
-export const ASSIGN = !!'4.0.0';
+export const ASSIGN = !!'4.0.0-beta.1';

packages/@ember/polyfills/index.ts

@@ -1,4 +1,3 @@
-// Export `assignPolyfill` for testing
-export { default as assign, assign as assignPolyfill } from './lib/assign';
+export { assign } from './lib/assign';
 
 export const hasPropertyAccessors = true;

packages/@ember/polyfills/lib/assign.ts

@@ -7,7 +7,7 @@ import { deprecate } from '@ember/debug';
 export function assign<T, U>(target: T, source: U): T & U;
 export function assign<T, U, V>(target: T, source1: U, source2: V): T & U & V;
 export function assign<T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W;
-export function assign(target: object, ...sources: any[]): any;
+export function assign(target: object, ...sources: object[]): object;
 /**
   Copy properties from a source object to a target object. Source arguments remain unchanged.
 
@@ -29,7 +29,7 @@ export function assign(target: object, ...sources: any[]): any;
   @public
   @static
 */
-export function assign(target: object) {
+export function assign(target: object): object {
   deprecate(
     'Use of `assign` has been deprecated. Please use `Object.assign` or the spread operator instead.',
     false,
@@ -44,26 +44,5 @@ export function assign(target: object) {
     }
   );
 
-  for (let i = 1; i < arguments.length; i++) {
-    let arg = arguments[i];
-    if (!arg) {
-      continue;
-    }
-
-    let updates = Object.keys(arg);
-
-    for (let i = 0; i < updates.length; i++) {
-      let prop = updates[i];
-      target[prop] = arg[prop];
-    }
-  }
-
-  return target;
+  return Object.assign(target, ...arguments);
 }
-
-// Note: We use the bracket notation so
-//       that the babel plugin does not
-//       transform it.
-// https://www.npmjs.com/package/babel-plugin-transform-object-assign
-const { assign: _assign } = Object;
-export default (_assign || assign) as typeof assign;

packages/@ember/polyfills/tests/assign_test.js

@@ -1,4 +1,4 @@
-import { assignPolyfill, assign } from '..';
+import { assign as assignPolyfill } from '..';
 import { moduleFor, AbstractTestCase as TestCase } from 'internal-test-helpers';
 
 class AssignTests extends TestCase {
@@ -55,12 +55,3 @@ moduleFor(
     }
   }
 );
-
-moduleFor(
-  'Ember.assign (maybe not-polyfill ;) )',
-  class extends AssignTests {
-    assign() {
-      return assign(...arguments);
-    }
-  }
-);

packages/ember/index.js

@@ -223,7 +223,7 @@ Ember.get = metal.get;
 Ember._getPath = metal._getPath;
 Ember.set = metal.set;
 Ember.trySet = metal.trySet;
-Ember.FEATURES = assign({ isEnabled }, FEATURES);
+Ember.FEATURES = Object.assign({ isEnabled }, FEATURES);
 Ember._Cache = utils.Cache;
 Ember.on = metal.on;
 Ember.addListener = metal.addListener;