IsNotNullImpl implements IsNotNull<T, R> { @Override public IsNull<T, R> negate() { return new IsNullImpl<>(expression); } IsNotNullImpl(ToNullable<T, R, ?> expression); @Override IsNull<T, R> negate(); @Override ToNullable<T, R, ?> expression();  }
@Test void negate() { assertTrue(instance.negate() instanceof IsNull); }