[BUGFIX beta] Fix proto return value for native classes

packages/ember-runtime/lib/system/core_object.js

@@ -241,15 +241,15 @@ function makeCtor(base) {
     };
   }
 
-  Class.willReopen = () => {
+  Class.willReopen = function() {
     if (wasApplied) {
       Class.PrototypeMixin = Mixin.create(Class.PrototypeMixin);
     }
 
     wasApplied = false;
   };
 
-  Class.proto = () => {
+  Class.proto = function() {
     let superclass = Class.superclass;
     if (superclass) {
       superclass.proto();
@@ -260,7 +260,10 @@ function makeCtor(base) {
       Class.PrototypeMixin.applyPartial(Class.prototype);
     }
 
-    return Class.prototype;
+    // Native classes will call the nearest superclass's proto function,
+    // and proto is expected to return the current instance's prototype,
+    // so we need to return it from `this` instead
+    return this.prototype;
   };
 
   return Class;

packages/ember-runtime/tests/system/object/es-compatibility-test.js

@@ -1,5 +1,5 @@
 import EmberObject from '../../../lib/system/object';
-import { Mixin } from 'ember-metal';
+import { Mixin, defineProperty, computed } from 'ember-metal';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 moduleFor(
@@ -277,5 +277,24 @@ moduleFor(
       assert.equal(obj.foo, 123, 'sets class fields on instance correctly');
       assert.equal(obj.bar, 789, 'sets passed in properties on instance correctly');
     }
+
+    ['@test calling metaForProperty on a native class works'](assert) {
+      assert.expect(0);
+
+      class SubEmberObject extends EmberObject {}
+
+      defineProperty(
+        SubEmberObject.prototype,
+        'foo',
+        computed('foo', {
+          get() {
+            return 'bar';
+          },
+        })
+      );
+
+      // able to get meta without throwing an error
+      SubEmberObject.metaForProperty('foo');
+    }
   }
 );