@GwtCompatible
@NullMarked
public abstract class MapInterfaceTest<K extends @Nullable Object, V extends @Nullable Object>
    extends TestCase {

  /** A key type that is not assignable to any classes but Object. */
  private static final class IncompatibleKeyType {
    @Override
    public String toString() {
      return "IncompatibleKeyType";
    }
  }

  protected final boolean supportsPut;

      return new Assignability<>();
    }
  }

  private static void assertAssignable(TypeToken<?> from, TypeToken<?> to) {
    assertTrue(
        from.getType() + " is expected to be assignable to " + to.getType(),
        to.isSupertypeOf(from));
    assertTrue(
        to.getType() + " is expected to be a supertype of " + from.getType(),
        to.isSupertypeOf(from));
    assertTrue(

      return new Assignability<>();
    }
  }

  private static void assertAssignable(TypeToken<?> from, TypeToken<?> to) {
    assertTrue(
        from.getType() + " is expected to be assignable to " + to.getType(),
        to.isSupertypeOf(from));
    assertTrue(
        to.getType() + " is expected to be a supertype of " + from.getType(),
        to.isSupertypeOf(from));
    assertTrue(

   */
  public static <V extends @Nullable Object> ListenableFuture<V> immediateFuture(
      @ParametricNullness V value) {
    if (value == null) {
      // This cast is safe because null is assignable to V for all V (i.e. it is bivariant)
      @SuppressWarnings("unchecked")
      ListenableFuture<V> typedNull = (ListenableFuture<V>) ImmediateFuture.NULL;
      return typedNull;
    }

pkg go/types, method (Checker) TypeOf(ast.Expr) Type
pkg go/types, method (Error) Error() string
pkg go/types, method (TypeAndValue) Addressable() bool
pkg go/types, method (TypeAndValue) Assignable() bool
pkg go/types, method (TypeAndValue) HasOk() bool
pkg go/types, method (TypeAndValue) IsBuiltin() bool
pkg go/types, method (TypeAndValue) IsNil() bool
pkg go/types, method (TypeAndValue) IsType() bool