MigrateInstance(target) before Object.assign(target, ...)

test/mjsunit/regress/regress-object-assign-deprecated-2.js

Index: test/mjsunit/regress/regress-object-assign-deprecated-2.js
diff --git a/test/message/arrow-invalid-rest-2.js b/test/mjsunit/regress/regress-object-assign-deprecated-2.js
similarity index 56%
copy from test/message/arrow-invalid-rest-2.js
copy to test/mjsunit/regress/regress-object-assign-deprecated-2.js
index 3517803d30256b09e78a1aa1f43817e733dc060e..89693de1a44cba5052f463665db61f1f9a4bf93e 100644
--- a/test/message/arrow-invalid-rest-2.js
+++ b/test/mjsunit/regress/regress-object-assign-deprecated-2.js
@@ -1,8 +1,8 @@
 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-//
-//
 
-var f = (a, ...x = 10) => x;
-f(1, 2, 3, 4, 5);
+var x = {a:1, b:2};
+Object.defineProperty(x, "c", {set(v) {}})
+var y = {get c() { return {a:1, b:2.5} }};
+Object.assign(x, y, x);