But there are plenty of static type systems that let different types share the same code, the problem you describe only exists in nominal type systems (like C++

But there are plenty of static type systems that let different types share the same code, the problem you describe only exists in nominal type systems (like C++) as far as I know. With structural types like in TypeScript or Go you can express this trivially. For that matter you can do this with subtype polymorphism in most cases. In Rust you can do it with trait objects as long as you control either the type or the trait. Probably there’s a way to do it in C++ too.