5009937: hiding versus generics versus binary compatibility

Summary: missing implementation of JLS 8.4.8.3 (different arguments with same erasure not always triggering a compiler error)
Reviewed-by: jjg

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

@@ -1247,7 +1247,7 @@ public class Check {
                 for (Type t2 = sup;
                      t2.tag == CLASS;
                      t2 = types.supertype(t2)) {
-                    for (Scope.Entry e2 = t1.tsym.members().lookup(s1.name);
+                    for (Scope.Entry e2 = t2.tsym.members().lookup(s1.name);
                          e2.scope != null;
                          e2 = e2.next()) {
                         Symbol s2 = e2.sym;
@@ -1394,6 +1394,16 @@ public class Check {
             while (e.scope != null) {
                 if (m.overrides(e.sym, origin, types, false))
                     checkOverride(tree, m, (MethodSymbol)e.sym, origin);
+                else if (e.sym.isInheritedIn(origin, types) && !m.isConstructor()) {
+                    Type er1 = m.erasure(types);
+                    Type er2 = e.sym.erasure(types);
+                    if (types.isSameType(er1,er2)) {
+                            log.error(TreeInfo.diagnosticPositionFor(m, tree),
+                                    "name.clash.same.erasure.no.override",
+                                    m, m.location(),
+                                    e.sym, e.sym.location());
+                    }
+                }
                 e = e.next();
             }
         }

test/tools/javac/generics/5009937/T5009937.java

+/*
+ * Copyright 2008 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 5009937
+ * @summary hiding versus generics versus binary compatibility
+ * @author Maurizio Cimadamore
+ *
+ * @compile/fail/ref=T5009937.out -XDstdout -XDrawDiagnostics T5009937.java
+ */
+
+public class T5009937<X> {
+    static class A {
+        static void m(T5009937<String> l) {}
+    }
+
+    static class B extends A {
+        static void m(T5009937<Integer> l) {}
+    }
+}

test/tools/javac/generics/5009937/T5009937.out

+T5009937.java:39:21: compiler.err.name.clash.same.erasure.no.override: m(T5009937<java.lang.Integer>), T5009937.B, m(T5009937<java.lang.String>), T5009937.A
+1 error

test/tools/javac/generics/InheritanceConflict.java

@@ -25,7 +25,7 @@
  * @test
  * @bug 4984158
  * @summary two inherited methods with same signature
- * @author gafter
+ * @author gafter, Maurizio Cimadamore
  *
  * @compile/fail -source 1.5 InheritanceConflict.java
  */
@@ -34,8 +34,11 @@ package inheritance.conflict;
 
 class A<T> {
     void f(String s) {}
+}
+
+class B<T> extends A<T> {
     void f(T t) {}
 }
 
-class B extends A<String> {
+class C extends B<String> {
 }

test/tools/javac/generics/InheritanceConflict2.java

@@ -25,7 +25,7 @@
  * @test
  * @bug 4984158
  * @summary two inherited methods with same signature
- * @author gafter
+ * @author gafter, Maurizio Cimadamore
  *
  * @compile -source 1.5 InheritanceConflict2.java
  */
@@ -34,9 +34,12 @@ package inheritance.conflict2;
 
 class A<T> {
     void f(String s) {}
+}
+
+class B<T> extends A<T> {
     void f(T t) {}
 }
 
-class B extends A<String> {
+class C extends B<String> {
     void f(String s) {}
 }