6557199: Fails to reject bad override of generic method

Summary: Javac does not correctly implement JLS3 8.4.5
Reviewed-by: jjg

src/share/classes/com/sun/tools/javac/code/Types.java

@@ -2933,32 +2933,16 @@ public class Types {
      * Language Specification, Third Ed. (8.4.5)</a>
      */
     public boolean returnTypeSubstitutable(Type r1, Type r2) {
+        return returnTypeSubstitutable(r1, r2, Warner.noWarnings);
+    }
+    //where
+    public boolean returnTypeSubstitutable(Type r1, Type r2, Warner warner) {
         if (hasSameArgs(r1, r2))
-            return resultSubtype(r1, r2, Warner.noWarnings);
+            return resultSubtype(r1, r2, warner);
         else
             return covariantReturnType(r1.getReturnType(),
-                                       erasure(r2.getReturnType()),
-                                       Warner.noWarnings);
-    }
-
-    public boolean returnTypeSubstitutable(Type r1,
-                                           Type r2, Type r2res,
-                                           Warner warner) {
-        if (isSameType(r1.getReturnType(), r2res))
-            return true;
-        if (r1.getReturnType().isPrimitive() || r2res.isPrimitive())
-            return false;
-
-        if (hasSameArgs(r1, r2))
-            return covariantReturnType(r1.getReturnType(), r2res, warner);
-        if (!source.allowCovariantReturns())
-            return false;
-        if (isSubtypeUnchecked(r1.getReturnType(), r2res, warner))
-            return true;
-        if (!isSubtype(r1.getReturnType(), erasure(r2res)))
-            return false;
-        warner.warnUnchecked();
-        return true;
+                                       r2.getReturnType(),
+                                       warner);
     }
 
     /**
@@ -2966,12 +2950,24 @@ public class Types {
      * method that returns s?
      */
     public boolean covariantReturnType(Type t, Type s, Warner warner) {
-        return
-            isSameType(t, s) ||
-            source.allowCovariantReturns() &&
+        //are return types identical?
+        if (isSameType(t, s))
+            return true;
+        //if t and s are both reference types...
+        else if(source.allowCovariantReturns() &&
             !t.isPrimitive() &&
-            !s.isPrimitive() &&
-            isAssignable(t, s, warner);
+            !s.isPrimitive()) {
+            //check that t is some unchecked subtype of s
+            if (isSubtypeUnchecked(t, s, warner))
+                return true;
+            //otherwise check that t = |s|
+            else if (isSameType(t, erasure(s))) {
+                warner.warnUnchecked();
+                return true;
+            }
+        }
+        //otherwise t is not return type substitutable for s
+        return false;
     }
     // </editor-fold>
 

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

@@ -1163,7 +1163,7 @@ public class Check {
 
         overrideWarner.warned = false;
         boolean resultTypesOK =
-            types.returnTypeSubstitutable(mt, ot, otres, overrideWarner);
+            types.covariantReturnType(mtres, otres, overrideWarner);
         if (!resultTypesOK) {
             if (!source.allowCovariantReturns() &&
                 m.owner != origin &&

test/tools/javac/generics/rawOverride/6557199/T6557199.java

+/*
+ * Copyright 2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug 6557199
+ * @summary  Fails to reject bad override of generic method
+ * @author Maurizio Cimadamore
+ * @compile/fail/ref=T6557199.out T6557199.java -XDrawDiagnostics
+ */
+
+class T6557199 {
+    static class X<S> {
+        public static <U> X<U> test() {
+            return null;
+        }
+    }
+
+    static class B extends X<B> {
+        public static B test() {
+            return null;
+        }
+    }
+}

test/tools/javac/generics/rawOverride/6557199/T6557199.out

+T6557199.java:40:25: compiler.err.prob.found.req: (- compiler.misc.override.incompatible.ret: (- compiler.misc.cant.override: test(), T6557199.B, <U>test(), T6557199.X)), T6557199.B, T6557199.X<U>
+1 error