void (Set<Set<X1>> t) { Set<Set<? extends X1>> t2 = <error descr="Inconvertible types; cannot cast 'java.util.Set<java.util.Set<InvalidCast.X1>>' to 'java.util.Set<java.util.Set<? extends InvalidCast.X1>>'">(Set<Set<? extends X1>>) t</error>; //error }