Java source compiles on ECLIPSE but fails on JDK 1.5 / 1.6

Java source compile on ECLOPSE but failiing on the latest
JDK for 1.5 and 1.6. The code does compile on JDK 7

Source code

public class Test2
{
   public static <T> void method( X<T> x, T t ) {}

   public void testCompile()
   {
       method( new X<Gen<String>>(), new Gen() ); //generates error in javac, not in Eclipse
   }

   private class Gen<T> {}
   private class X<T> extends Gen<T> {}
}

cores2-da-sparc-2-a:/cores_data/pool-1/data4/3-2695544290 23 % /usr/jdk/jdk1.6.0_21/bin/java -version
java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) Server VM (build 17.0-b16, mixed mode)

cores2-da-sparc-2-a:/cores_data/pool-1/data4/3-2695544290 25 % /usr/jdk/jdk1.6.0_21/bin/javac Test2.java
Test2.java:7: <T>method(Test2.X<T>,T) in Test2 cannot be applied to (Test2.X<Test2.Gen<java.lang.String>>,Test2.Gen)
               method( new X<Gen<String>>(), new Gen() ); //generates error in javac, not in Eclipse
               ^
1 error
This escalated CR is being worked via CR 6718364