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But I thought you could cast a raw pointer to a reference with "as" in an unsafe block? Obviously that makes it possible for you to create multiple mutable refe

But I thought you could cast a raw pointer to a reference with "as" in an unsafe block? Obviously that makes it possible for you to create multiple mutable references, or a mutable reference at the same time as an immutable reference, which is undefined behaviour, but undefined behaviour was always going to be the risk of this idea. Also, even if you had a compiler switch to make "unsafe" implicit everywhere, your code is going to be littered with a lot of casts. (Obviously I'm not a Rust expert, which is why my comments are in the form of questions.)

steveklabnik 6y ago
Nah it's all good! This is a pretty common thing, and sometimes comes in an alternate form ("can't you just Arc all the things?") You can cast them to a reference. The issue is, the tricky UB happens at this exact boundary. If you're only using references, then the compiler has your back. If you're only using raw pointers, then there are no aliasing issues, so you're good. The hardest part is exactly the boundary between the two. Staying in one world or the other is much easier than going back and forth.