8023945: javac wrongly allows a subclass of an anonymous class

Reviewed-by: jjg

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

@@ -812,6 +812,10 @@ public class Attr extends JCTree.Visitor {
                    boolean classExpected,
                    boolean interfaceExpected,
                    boolean checkExtensible) {
+        if (t.tsym.isAnonymous()) {
+            log.error(tree.pos(), "cant.inherit.from.anon");
+            return types.createErrorType(t);
+        }
         if (t.isErroneous())
             return t;
         if (t.hasTag(TYPEVAR) && !classExpected && !interfaceExpected) {

src/share/classes/com/sun/tools/javac/resources/compiler.properties

@@ -123,6 +123,9 @@ compiler.err.anon.class.impl.intf.no.typeargs=\
 compiler.err.anon.class.impl.intf.no.qual.for.new=\
     anonymous class implements interface; cannot have qualifier for new
 
+compiler.err.cant.inherit.from.anon=\
+    cannot inherit from anonymous class
+
 # 0: symbol, 1: symbol, 2: symbol
 compiler.err.array.and.varargs=\
     cannot declare both {0} and {1} in {2}

test/tools/javac/AnonymousSubclassTest.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 8023945
+ * @summary javac wrongly allows a subclass of an anonymous class
+ * @library /tools/javac/lib
+ * @build ToolBox
+ * @run main AnonymousSubclassTest
+ */
+
+import java.util.ArrayList;
+import java.io.IOException;
+
+public class AnonymousSubclassTest {
+    public static void main(String... args) throws Exception {
+        new AnonymousSubclassTest().run();
+    }
+
+    // To trigger the error we want, first we need to compile
+    // a class with an anonymous inner class: Foo$1.
+    final String foo =
+        "public class Foo {" +
+        "  void m() { Foo f = new Foo() {}; }" +
+        "}";
+
+    // Then, we try to subclass the anonymous class
+    // Note: we must do this in two classes because a different
+    // error will be generated if we don't load Foo$1 through the
+    // class reader.
+    final String test1 =
+        "public class Test1 {" +
+        "  void m() {"+
+        "    Foo f1 = new Foo();"+
+        "    Foo f2 = new Foo$1(f1) {};"+
+        "  }" +
+        "}";
+
+    final String test2 =
+        "public class Test2 {" +
+        "  class T extends Foo$1 {" +
+        "    public T(Foo f) { super(f); }" +
+        "  }"+
+        "}";
+
+    void compOk(String code) throws Exception {
+        ToolBox.javac(new ToolBox.JavaToolArgs().setSources(code));
+    }
+
+    void compFail(String code) throws Exception {
+        ArrayList<String> errors = new ArrayList<>();
+        ToolBox.JavaToolArgs args = new ToolBox.JavaToolArgs();
+        args.setSources(code)
+            .appendArgs("-cp", ".", "-XDrawDiagnostics")
+            .set(ToolBox.Expect.FAIL)
+            .setErrOutput(errors);
+        ToolBox.javac(args);
+
+        if (!errors.get(0).contains("cant.inherit.from.anon")) {
+            System.out.println(errors.get(0));
+            throw new Exception("test failed");
+        }
+    }
+
+    void run() throws Exception {
+        compOk(foo);
+        compFail(test1);
+        compFail(test2);
+    }
+}

test/tools/javac/diags/examples.not-yet.txt

@@ -110,4 +110,4 @@ compiler.warn.unexpected.archive.file                   # Paths: zip file with u
 compiler.warn.unknown.enum.constant                     # in bad class file
 compiler.warn.unknown.enum.constant.reason              # in bad class file
 compiler.warn.override.equals.but.not.hashcode          # when a class overrides equals but not hashCode method from Object
-
+compiler.err.cant.inherit.from.anon                     # error for subclass of anonymous class