Baffling Interface Casting - How is this supposed to work

Question

I am trying to cast one interface to another. You can cast one interface to another if all the method signatures and return types in the "to" interface apprear in the "from" interface.
I am confused as to what should happen if the return type is the interface itself. for example
package rob;
public interface Test {
     public Test foo();
should I be able to cast this to
package foo;
public interface Test {
     public Test foo();
The reason that I am confused is that if I use Eclipse to compile, it works, however under JDK 1.3.1 I get the following error
C:\workspace\Cast>c:\jdk1.3.1\bin\javac Tester.java
Tester.java:26: interfaces foo.Test and rob.Test are incompatible; both define foo(), but with different return type
rob.Test var = (rob.Test)foo();
^
1 error
We have worked around this issue, but I am interested in knowing what the correct answer is. The language specification is a little vague in this point. It states that if the return types of a method are different then the incompatable error should be seen at compile time.
While I agree that rob.Test is different to foo.Test a return type of Self should be dealt with differently shouldn't it ?
If anyone knows the right answer, or why this works in Eclipse please let me know
Many Thanks

Answer 1

You can cast one interface to another if all the method signatures
and return types in the "to" interface apprear in the "from" interface.Sorry, this sentence is not correct!
You could check the Java language Specification.
In fact, the 2 interface you wrote are totally different, even
they contents exacte method signiture.
rob.Test and foo.Test are 2 things, and no compatible.