8240299: A possible bug about Object.setPrototypeOf().

src/org.openjdk.nashorn/share/classes/org/openjdk/nashorn/internal/objects/NativeObject.java

@@ -204,15 +204,15 @@ public static Object getPrototypeOf(final Object self, final Object obj) {
      */
     @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR)
     public static Object setPrototypeOf(final Object self, final Object obj, final Object proto) {
+        Global.checkObjectCoercible(self);
+
         if (obj instanceof ScriptObject) {
             ((ScriptObject)obj).setPrototypeOf(proto);
-            return obj;
         } else if (obj instanceof ScriptObjectMirror) {
             ((ScriptObjectMirror)obj).setProto(proto);
-            return obj;
         }
 
-        throw notAnObject(obj);
+        return obj;
     }
 
     /**

test/nashorn/script/basic/JDK-8240299.js

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * JDK-8240299: Object.setPrototypeOf() should silently be no-op on non-objects
+ *
+ * @test
+ * @run
+ */
+
+var foo = function(){ 
+    var a = Object.setPrototypeOf("test", null); 
+    print(a); 
+}; 
+foo(); 

test/nashorn/script/basic/JDK-8240299.js.EXPECTED

@@ -0,0 +1 @@
+test