Here&#x27;s another example with less trivial breakage, which was reverted:<p><a href="https:&#x2F;&#x2F;www.fxsitecompat.com&#x2F;en-US&#x2F;docs&#x2F;2015&#x2F;string-prototype-contains-has-been-renamed-to-includes&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.fxsitecompat.com&#x2F;en-US&#x2F;docs&#x2F;2015&#x2F;string-prototyp...</a><p>Unless you mean to refute the idea that JS doesn&#x27;t break <i>anything ever</i> - which it clearly does, <i>occasionally</i>, but proof-of-concept golf code that intentionally takes fragile shortcuts isn&#x27;t the best example.<p>...But JS has moved away from monkey patching builtin objects for good reason, whereas Rust tends to be relatively promiscuous in adding methods to other people&#x27;s types via trait impls.  This isn&#x27;t bad per se, but I do think it creates bigger compatibility risks.