FULL PRODUCT VERSION :


A DESCRIPTION OF THE PROBLEM :
Compiling the provided java snippet should yield a unchecked cast warning

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile code code using javac

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
unchecked cast warning
ACTUAL -
no warning

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package a;

public class CastTest {
public interface BaseInterface<T> {

}

public interface SubInterfaceA<T> extends BaseInterface<T> {

}

public interface SubInterfaceB<T> extends BaseInterface<T> {

}

public static void main(String[] args) {
SubInterfaceA<String> a = null;
SubInterfaceB<String> b = (SubInterfaceB<String>) a; // javac does not warn
b = (SubInterfaceB<String>)(BaseInterface<String>)a;

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

also discussed in compiler-dev: http://mail.openjdk.java.net/pipermail/compiler-dev/2014-May/008747.html