checker/tests/nullness/generics/GenericsBounds5.java

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

public class GenericsBounds5 {
  class Collection1<E extends @Nullable Object> {
    public void add(E elt) {
      // This call is forbidden, because elt might be null.
      // :: error: (dereference.of.nullable)
      elt.hashCode();
    }
  }

  <@Nullable F extends @Nullable Object> void addNull1(Collection1<F> l) {
    // This call is allowed, because F is definitely @Nullable.
    l.add(null);
  }

  // Effectively, this should be the same signature as above.
  // TODO: the type "@Nullable ?" is "@Nullable ? extends @NonNull Object",
  // with the wrong extends bound.
  void addNull2(Collection1<@Nullable ? extends @Nullable Object> l) {
    // This call has to pass, like above.
    l.add(null);
  }

  <@Nullable F extends @Nullable Object> void addNull3(Collection1<F> l, F p) {
    // This call is allowed, because F is definitely @Nullable.
    l.add(null);
    l.add(p);
  }

  // :: error: (assignment)
  Collection1<@Nullable ? extends @Nullable Integer> f = new Collection1<@NonNull Integer>();

  void bad(Collection1<@NonNull Integer> nnarg) {
    // These have to be forbidden, because f1 might refer to a
    // collection that has NonNull as type argument.
    // :: error: (type.argument)
    addNull1(nnarg);

    // :: error: (argument)
    addNull2(nnarg);

    // :: error: (type.argument)
    addNull3(nnarg, Integer.valueOf(4));
  }
}