import java.util.Collection; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.function.Function; class Test { { final Map<Comparable, List<Collection<?>>> families = sortingMerge(<error descr="Incompatible equality constraint: Integer and Comparable">(s) -> 0</error>); } private <C extends Comparable<C>, T> Map<C, List<T>> sortingMerge(Function<T, C> keyFunction) { return new HashMap<C, List<T>>(); } }