--- a/langtools/src/share/classes/com/sun/tools/javac/processing/JavacFiler.java	Thu Jul 29 15:57:43 2010 +0100
+++ b/langtools/src/share/classes/com/sun/tools/javac/processing/JavacFiler.java	Thu Jul 29 18:06:34 2010 -0700
@@ -379,6 +379,15 @@
     }
 
     private JavaFileObject createSourceOrClassFile(boolean isSourceFile, String name) throws IOException {
+        if (lint) {
+            int periodIndex = name.lastIndexOf(".");
+            if (periodIndex != -1) {
+                String base = name.substring(periodIndex);
+                String extn = (isSourceFile ? ".java" : ".class");
+                if (base.equals(extn))
+                    log.warning("proc.suspicious.class.name", name, extn);
+            }
+        }
         checkNameAndExistence(name, isSourceFile);
         Location loc = (isSourceFile ? SOURCE_OUTPUT : CLASS_OUTPUT);
         JavaFileObject.Kind kind = (isSourceFile ?

--- a/langtools/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Thu Jul 29 15:57:43 2010 +0100
+++ b/langtools/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Thu Jul 29 18:06:34 2010 -0700
@@ -778,6 +778,9 @@
 compiler.warn.proc.illegal.file.name=\
     Cannot create file for illegal name ''{0}''.
 
+compiler.warn.proc.suspicious.class.name=\
+    Creating file for a type whose name ends in {1}: ''{0}''
+
 compiler.warn.proc.file.create.last.round=\
     File for type ''{0}'' created in the last round will not be subject to annotation processing.
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/ProcSuspiciousClassName/ProcSuspiciousClassName.java	Thu Jul 29 18:06:34 2010 -0700
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2010, 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.
+ */
+
+// key: compiler.warn.proc.suspicious.class.name
+// options: -Xlint:processing -processor AnnoProc
+
+class ProcSuspiciousClassName { }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/diags/examples/ProcSuspiciousClassName/processors/AnnoProc.java	Thu Jul 29 18:06:34 2010 -0700
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2010, 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.
+ */
+
+import java.io.*;
+import java.util.*;
+import javax.annotation.processing.*;
+import javax.lang.model.*;
+import javax.lang.model.element.*;
+import javax.tools.*;
+
+@SupportedAnnotationTypes("*")
+public class AnnoProc extends AbstractProcessor {
+    public boolean process(Set<? extends TypeElement> elems, RoundEnvironment renv) {
+        if (++round == 1) {
+            Filer filer = processingEnv.getFiler();
+            Messager messager = processingEnv.getMessager();
+            try {
+                FileObject fo = filer.createSourceFile("HelloWorld.java");
+                try (Writer out = fo.openWriter()) {
+                    out.write("class HelloWorld {\n");
+                    out.write("  public static void main(String[] args) {\n");
+                    out.write("    System.out.println(\"Hello World!\");\n");
+                    out.write("  }\n");
+                    out.write("}\n");
+                }
+            } catch (IOException e) {
+                messager.printMessage(Diagnostic.Kind.ERROR, e.toString());
+            }
+        }
+        return false;
+    }
+
+    public SourceVersion getSupportedSourceVersion() {
+        return SourceVersion.latest();
+    }
+
+    int round = 0;
+}