The new rewrite rules invalidate the following snippet of code from ConcurrentHashMap.java.

    public void putAll(Map<? extends K, ? extends V> t) {
        Iterator<Map.Entry<? extends K, ? extends V>> it = t.entrySet().iterator();
        while (it.hasNext()) {
            Entry<? extends K, ? extends V> e = it.next();
            put(e.getKey(), e.getValue());
        }
    }

==========$ cat T.java
import java.util.*;

class Main<K, V> {
    public void main(Map<? extends K, ? extends V> t) {
        Iterator<Map.Entry<? extends K, ? extends V>> it = t.entrySet().iterator();
    }
}
==========$ newjavac T.java
+ exec /usr/java1.5/bin/javac -J-esa -source 1.5 -target 1.4 T.java
T.java:5: incompatible types
found : ? extends java.util.Iterator<? extends java.util.Map.Entry<? extends K,? extends V>>
required: java.util.Iterator<java.util.Map.Entry<? extends K,? extends V>>
        Iterator<Map.Entry<? extends K, ? extends V>> it = t.entrySet().iterator();
                                                                                ^
1 error
==========$