知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 @MarkusMeskanen: because the object is immutable, and if you mutated it in place you could possibly not specialise it in the subclass. This was noticed by Khushal Bherwani who posted an instance on X, I am capable to duplicate it, Here's my GIF of it in motion: https://residentialpropertygurugram.design.blog/