The implementations of this type of thing in Rust I've seen just use "unsafe" everywhere. Even in strict C++ it is tricky to express the dynamic resolution of p

The implementations of this type of thing in Rust I've seen just use "unsafe" everywhere. Even in strict C++ it is tricky to express the dynamic resolution of pointer type correctly. Type punning is a bad idea but there also weren't many alternatives so that was the idiom everyone used for a long time. Bugs do occur due to this, so the admonition against type punning has a purpose. It can be done without strict aliasing violations in C++, but the methods were a bit arcane until quite recently. These scenarios cause other problems for Rust e.g. DMA hardware tacitly holds an invisible mutable reference to objects, but most developers never have to deal with cases like this. C++ provides some tools to annotate the code so that the compiler understands it cannot see all references to an object or that the lifetime is ambiguous. This type of code is not common but high-performance storage engines are kind of a perfect storm of architectural requirements that break the core Rust invariants.