8078414: Don't create impossible converters for ScriptObjectMirror

Reviewed-by: hannesw, sundar

nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/linker/NashornLinker.java

@@ -216,10 +216,11 @@ final class NashornLinker implements TypeBasedGuardingDynamicLinker, GuardingTyp
         // Could've also used (targetType.isAssignableFrom(ScriptObjectMirror.class) && targetType != Object.class) but
         // it's probably better to explicitly spell out the supported target types
         if (targetType == Map.class || targetType == Bindings.class || targetType == JSObject.class || targetType == ScriptObjectMirror.class) {
-            if(ScriptObject.class.isAssignableFrom(sourceType)) {
+            if (ScriptObject.class.isAssignableFrom(sourceType)) {
                 return new GuardedInvocation(CREATE_MIRROR);
+            } else if (sourceType.isAssignableFrom(ScriptObject.class) || sourceType.isInterface()) {
+                return new GuardedInvocation(CREATE_MIRROR, IS_SCRIPT_OBJECT);
             }
-            return new GuardedInvocation(CREATE_MIRROR, IS_SCRIPT_OBJECT);
         }
         return null;
     }

nashorn/test/src/jdk/nashorn/internal/runtime/test/JDK_8078414_Test.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2015, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package jdk.nashorn.internal.runtime.test;
+
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.assertTrue;
+
+import java.util.Map;
+import javax.script.Bindings;
+import jdk.nashorn.api.scripting.JSObject;
+import jdk.nashorn.api.scripting.ScriptObjectMirror;
+import jdk.nashorn.internal.objects.NativeArray;
+import jdk.nashorn.internal.runtime.ScriptObject;
+import jdk.nashorn.internal.runtime.linker.Bootstrap;
+import org.testng.annotations.Test;
+
+/**
+ * @test
+ * @bug 8078414
+ * @summary Test that arbitrary classes can't be converted to mirror's superclasses/interfaces.
+ * @run testng jdk.nashorn.internal.runtime.test.JDK_8078414_Test
+ */
+public class JDK_8078414_Test {
+    @Test
+    public void testCanNotConvertArbitraryClassToMirror() {
+        assertCanNotConvert(Double.class, Map.class);
+        assertCanNotConvert(Double.class, Bindings.class);
+        assertCanNotConvert(Double.class, JSObject.class);
+        assertCanNotConvert(Double.class, ScriptObjectMirror.class);
+    }
+
+    @Test
+    public void testCanConvertObjectToMirror() {
+        assertCanConvertToMirror(Object.class);
+    }
+
+    @Test
+    public void testCanConvertScriptObjectToMirror() {
+        assertCanConvertToMirror(ScriptObject.class);
+    }
+
+    @Test
+    public void testCanConvertScriptObjectSubclassToMirror() {
+        assertCanConvertToMirror(NativeArray.class);
+    }
+
+    @Test
+    public void testCanConvertArbitraryInterfaceToMirror() {
+        // We allow arbitrary interface classes, depending on what implements them, to end up being
+        // convertible to ScriptObjectMirror, as an implementation can theoretically pass an
+        // "instanceof ScriptObject" guard.
+        assertCanConvertToMirror(TestInterface.class);
+    }
+
+    public static interface TestInterface {
+    }
+
+    private static boolean canConvert(final Class<?> from, final Class<?> to) {
+        return Bootstrap.getLinkerServices().canConvert(from, to);
+    }
+
+    private static void assertCanConvert(final Class<?> from, final Class<?> to) {
+        assertTrue(canConvert(from, to));
+    }
+
+    private static void assertCanNotConvert(final Class<?> from, final Class<?> to) {
+        assertFalse(canConvert(from, to));
+    }
+
+    private static void assertCanConvertToMirror(final Class<?> from) {
+        assertCanConvert(from, Map.class);
+        assertCanConvert(from, Bindings.class);
+        assertCanConvert(from, JSObject.class);
+        assertCanConvert(from, ScriptObjectMirror.class);
+    }
+}