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