--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/generics/Nonlinear.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,125 @@
+/*
+ * Copyright 2001-2007 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 4607420
+ * @summary A bug in the original JSR14 generics specification
+ *          created a loophole in the type system.
+ *
+ * @compile/fail -source 1.5 Nonlinear.java
+ */
+
+
+public class Nonlinear {
+
+    // This is an example of lack of type safety for
+    // the version of javac from jsr14_adding_generics-1_0-ea
+
+    // It is a variant of the "classic" problem with polymorphic
+    // references in SML, which resulted in the usual array of
+    // fixes: notably value polymorphism.
+
+    // This code compiles, but produces a ClassCastException
+    // when executed, even though there are no explicit casts in
+    // the program.
+
+    public static void main (String [] args) {
+        Integer x = new Integer (5);
+        String y = castit (x);
+        System.out.println (y);
+    }
+
+    static <A,B> A castit (B x) {
+        // This method casts any type to any other type.
+        // Oh dear.  This shouldn't type check, but does
+        // because build () returns a type Ref<*>
+        // which is a subtype of RWRef<A,B>.
+        final RWRef<A,B> r = build ();
+        r.set (x);
+        return r.get ();
+    }
+
+    static <A> Ref<A> build () {
+        return new Ref<A> ();
+    }
+
+    // Another way of doing this is a variant of the crackit
+    // example discussed in the draft specification.
+    //
+    // The original duplicate was:
+    //
+    // static <A> Pair <A,A> duplicate (A x) {
+    //     return new Pair<A,A> (x,x);
+    // }
+    //
+    // which breaks the requirement that a type variable
+    // instantiated by * only occurs once in the result type.
+    //
+    // However, we can achieve the same result with a different
+    // type for duplicate, which uses its type variables linearly
+    // in the result:
+
+    static <A,B extends Ref<A>> Pair<Ref<A>,B> duplicate (B x) {
+        return new Pair<Ref<A>,B> (x,x);
+    }
+
+    // the cheat here is that A and B are used linearly in the result
+    // type, but not in the polymorphic bounds.
+
+    // We can use that to give an alternative implementation of
+    // castit.
+
+    static <A,B> A castit2 (B x) {
+        Pair <Ref<A>, Ref<B>> p = duplicate (build ());
+        p.snd.set (x);
+        return p.fst.get ();
+    }
+
+
+}
+
+interface RWRef<A,B> {
+
+    public A get ();
+    public void set (B x);
+
+}
+
+class Ref<A> implements RWRef <A,A> {
+
+    A contents;
+
+    public void set (A x) { contents = x; }
+    public A get () { return contents; }
+
+}
+
+class Pair<A,B> {
+
+    final A fst;
+    final B snd;
+
+    Pair (A fst, B snd) { this.fst = fst; this.snd = snd; }
+
+}