8015101: Covariance of return type implied by upper bounding on type parameter is ignored

Summary: Capture intersection supertypes before comparing their members
Reviewed-by: vromero

src/share/classes/com/sun/tools/javac/comp/Check.java

@@ -1813,6 +1813,11 @@ public class Check {
                                             Type t1,
                                             Type t2,
                                             Type site) {
+        if ((site.tsym.flags() & COMPOUND) != 0) {
+            // special case for intersections: need to eliminate wildcards in supertypes
+            t1 = types.capture(t1);
+            t2 = types.capture(t2);
+        }
         return firstIncompatibility(pos, t1, t2, site) == null;
     }
 

test/tools/javac/generics/wildcards/7034495/T7034495.out

-T7034495.java:40:17: compiler.err.types.incompatible.diff.ret: T7034495.B<?>, T7034495.A<?>, foo()
+T7034495.java:40:17: compiler.err.types.incompatible.diff.ret: T7034495.B<compiler.misc.type.captureof: 1, ?>, T7034495.A<compiler.misc.type.captureof: 2, ?>, foo()
 1 error

test/tools/javac/generics/wildcards/T8015101.java

+/*
+ * Copyright (c) 2014, 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 8015101
+ * @summary Mishandling of wildcards in intersection member method check
+ * @compile T8015101.java
+ */
+class T8015101 {
+
+     public static class Bug<X extends Child<?, ?> & Runnable> {
+     }
+
+     interface Parent<C> {
+         public C get();
+     }
+
+     interface Child<C, S extends C> extends Parent<C> {
+         @Override
+         public S get();
+     }
+
+ }