8174840: Elements.overrides does not check the return type of the methods

Co-authored-by: Pavel Rappo <[email protected]>
Reviewed-by: liach, darcy

Author: nizarbenalla

src/java.compiler/share/classes/javax/lang/model/util/Elements.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2025, 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
@@ -778,6 +778,12 @@ default TypeElement getOutermostTypeElement(Element e) {
      *                           elements.getTypeElement("I"));
      * }
      *
+     * @apiNote This method examines the method's name, signature, subclass relationship, and accessibility
+     * in determining whether one method overrides another, as specified in JLS {@jls 8.4.8.1}.
+     * In addition, an implementation may have stricter checks including method modifiers, return types and
+     * exception types as described in JLS {@jls 8.4.8.1} and {@jls 8.4.8.3}.
+     * Note that such additional compile-time checks are not guaranteed and may vary between implementations.
+     *
      * @param overrider  the first method, possible overrider
      * @param overridden  the second method, possibly being overridden
      * @param type   the class or interface of which the first method is a member

test/langtools/tools/javac/processing/model/util/elements/overrides/S.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2023, 2025, 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.
+ */
+
+/*
+ * This file models a few cases where Elements.overrides produces a false
+ * positive which warrants @apiNote.
+ */
+
+// S.java does not compile because it violates the JLS rules for overrides
+class S {
+
+    public void m() { }
+}
+
+// `protected` is a weaker modifier than `public`
+class T1 extends S {
+
+    protected void m() { }
+}
+
+// `package-private` is a weaker modifier than `public`
+class T2 extends S {
+
+    void m() { }
+}
+
+// `private` methods cannot override public method
+class T3 extends S {
+
+    private void m() { }
+}
+
+// return type int is not compatible with void
+class T4 extends S {
+
+    public int m() { return 0; }
+}
+
+// adding a checked exception violates the override rule
+class T5 extends S {
+
+    public void m() throws Exception { }
+}

test/langtools/tools/javac/processing/model/util/elements/overrides/TestOverrides.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2023, 2025, 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 8174840
+ * @library /tools/javac/lib
+ * @build   JavacTestingAbstractProcessor TestOverrides
+ * @compile -processor TestOverrides -proc:only S.java
+ */
+
+import java.util.Set;
+import javax.annotation.processing.RoundEnvironment;
+import javax.lang.model.element.ExecutableElement;
+import javax.lang.model.element.TypeElement;
+
+import static javax.lang.model.element.ElementKind.METHOD;
+
+public class TestOverrides extends JavacTestingAbstractProcessor {
+
+    @Override
+    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment round) {
+        if (!round.processingOver()) {
+            var sm = mIn(elements.getTypeElement("S"));
+            for (var subtypeName : new String[]{"T1", "T2", "T3", "T4", "T5"}) {
+                var t = elements.getTypeElement(subtypeName);
+                var tm = mIn(t);
+                if (!elements.overrides(tm, sm, t))
+                    messager.printError(String.format(
+                            "%s does not override from %s method %s", tm, t.getQualifiedName(), sm));
+            }
+        }
+        return true;
+    }
+
+    private ExecutableElement mIn(TypeElement t) {
+        return t.getEnclosedElements().stream()
+                .filter(e -> e.getKind() == METHOD)
+                .filter(e -> e.getSimpleName().toString().equals("m"))
+                .map(e -> (ExecutableElement) e)
+                .findAny()
+                .get();
+    }
+}