FULL PRODUCT VERSION :
java version "1.6.0_33"
Java(TM) SE Runtime Environment (build 1.6.0_33-b03-424-10M3720)
Java HotSpot(TM) 64-Bit Server VM (build 20.8-b03-424, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Darwin Kernel Version 10.8.0: Tue Jun 7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386

A DESCRIPTION OF THE PROBLEM :
Trying to compile this code:
   public interface A {
       A getIt();
   }

   public interface B {
       B getIt();
   }

   public interface C extends A, B {
       @Override
       C getIt();
   }

I get an error:
types data.B and data.A are incompatible; both define getIt(), but with unrelated return types


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a file ComplexHierarchy.java with the following contents:
=====
package data;

public class ComplexHierarchy {
    public interface A {
        A getIt();
    }

    public interface B {
        B getIt();
    }

    public interface C extends A, B {
        @Override
        C getIt();
    }

}
====

Try to compile. Get the error

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No error should be reported (according to my understanding of the JLS)
ACTUAL -
Error:
types data.B and data.A are incompatible; both define getIt(), but with unrelated return types

ERROR MESSAGES/STACK TRACES THAT OCCUR :
types data.B and data.A are incompatible; both define getIt(), but with unrelated return types


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package data;

public class ComplexHierarchy {
    public interface A {
        A getIt();
    }

    public interface B {
        B getIt();
    }

    public interface C extends A, B {
        @Override
        C getIt();
    }

}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Use ecj