checker/tests/nullness/generics/CollectionsAnnotationsMin.java

import org.checkerframework.checker.nullness.qual.*;

public class CollectionsAnnotationsMin {
  static class Collection1<E extends @Nullable Object> {
    public void add(E elt) {
      // :: error: (dereference.of.nullable)
      elt.hashCode();
    }
  }

  static class PriorityQueue1<E extends @NonNull Object> extends Collection1<E> {
    public void add(E elt) {
      // dereference allowed here
      elt.hashCode();
    }
  }

  // This is allowed, as "null" cannot be added to f1
  static Collection1<? extends @Nullable Object> f1 = new PriorityQueue1<@NonNull Object>();

  // :: error: (assignment)
  static Collection1<@Nullable Object> f2 = new PriorityQueue1<@NonNull Object>();

  static void addNull1(Collection1<@Nullable Object> l) {
    l.add(null);
  }

  // The upper bound on E is implicitly from Collection1
  static <E extends @Nullable Object> void addNull2(Collection1<E> l) {
    // :: error: (argument)
    l.add(null);
  }

  // The upper bound on E is implicitly from Collection1
  static <E extends @Nullable Object> E addNull2b(Collection1<E> l, E p) {
    // :: error: (argument)
    l.add(null);
    return p;
  }

  static <@Nullable E extends @Nullable Object> void addNull3(Collection1<E> l) {
    l.add(null);
  }

  static void bad() {
    // :: error: (argument)
    addNull1(new PriorityQueue1<@NonNull Object>());

    addNull2(new PriorityQueue1<@NonNull Object>());
    addNull2b(new PriorityQueue1<@NonNull Object>(), new Object());

    // :: error: (type.argument)
    addNull3(new PriorityQueue1<@NonNull Object>());

    // :: error: (argument)
    f1.add(null);
  }
}