8268148: unchecked warnings handle ? and ? extends Object differently

Reviewed-by: jlahoda

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java

@@ -877,7 +877,9 @@ public boolean isExtendsBound() {
                 kind == UNBOUND;
         }
         public boolean isUnbound() {
-            return kind == UNBOUND;
+            // is it `?` or `? extends Object`?
+            return kind == UNBOUND ||
+                    (kind == EXTENDS && type.tsym.flatName() == type.tsym.name.table.names.java_lang_Object);
         }
 
         @Override

test/langtools/tools/javac/generics/inference/8176534/T8176534.out

@@ -1,8 +1,7 @@
 T8176534.java:12:43: compiler.warn.unchecked.meth.invocation.applied: kindname.method, forEnumeration, java.util.Enumeration<T>, java.util.Enumeration, kindname.class, T8176534
 T8176534.java:12:44: compiler.warn.prob.found.req: (compiler.misc.unchecked.assign), java.util.Enumeration, java.util.Enumeration<T>
 T8176534.java:12:28: compiler.warn.unchecked.meth.invocation.applied: kindname.method, newArrayList, java.util.Iterator<? extends E>, java.util.Iterator, kindname.class, T8176534
-T8176534.java:12:43: compiler.warn.prob.found.req: (compiler.misc.unchecked.assign), java.util.Iterator, java.util.Iterator<? extends E>
 T8176534.java:12:28: compiler.warn.prob.found.req: (compiler.misc.unchecked.assign), java.util.ArrayList, java.util.List<java.lang.String>
 - compiler.err.warnings.and.werror
 1 error
-5 warnings
+4 warnings

test/langtools/tools/javac/warnings/UnboundAndBoundByObjectTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021, 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.
+ */
+
+/*
+ * @test
+ * @bug 8268148
+ * @summary unchecked warnings handle ? and ? extends Object differently
+ * @compile -Xlint:all -Werror UnboundAndBoundByObjectTest.java
+ */
+
+import java.util.List;
+
+class UnboundAndBoundByObjectTest {
+    void f(List<? extends Object> x) {}
+    void g(List<?> x) {}
+
+    void h(List<String> x) {
+        f((List) x);
+        g((List) x);
+    }
+}