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import org.checkerframework.checker.nullness.qual.*;
// This is how I propose the Collection interface be annotated:
interface Collection1<E extends @Nullable Object> {
public void add(E elt);
}
class PriorityQueue1<E extends @NonNull Object> implements Collection1<E> {
public void add(E elt) {
// just to dereference elt
elt.hashCode();
}
}
class PriorityQueue2<E extends @NonNull Object> implements Collection1<E> {
public void add(E elt) {
// just to dereference elt
elt.hashCode();
}
}
// This is how the Collection interface is currently annotated
interface Collection2<E extends @NonNull Object> {
public void add(E elt);
}
class PriorityQueue3<E extends @NonNull Object> implements Collection2<E> {
public void add(E elt) {
// just to dereference elt
elt.hashCode();
}
}
class Methods {
static void addNull1(Collection1 l) {
// Allowed, because upper bound of Collection1 is Nullable.
// :: warning: [unchecked] unchecked call to add(E) as a member of the raw type Collection1
l.add(null);
}
static void bad1() {
addNull1(new PriorityQueue1());
}
// If the types are parameterized (as they should be)
static <@Nullable E extends @Nullable Object> void addNull2(Collection1<E> l) {
l.add(null);
}
static void bad2() {
// :: error: (type.argument.type.incompatible)
addNull2(new PriorityQueue1<@NonNull Object>());
}
public static void main(String[] args) {
bad2();
}
static void bad3() {
// :: error: (type.argument.type.incompatible)
addNull2(new PriorityQueue2<@NonNull Object>());
}
// :: error: (type.argument.type.incompatible)
static <@Nullable E> void addNull3(Collection2<E> l) {
l.add(null);
}
}
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