> Is this backwards? If B consumes data from A then to me that does not imply that A depends on anything from B; for a more concrete example that sentence reads

> Is this backwards? If B consumes data from A then to me that does not imply that A depends on anything from B; for a more concrete example that sentence reads to me like A is basically "throwing data over the wall" to B and whatever B does with said data is of no relevance to A. As a result, if B changes that shouldn't affect A. This is a specifically crafted bad idea, but you could have module A use unsafe to craft a Vec<u8> that is safe to use to read or write, but not to grow or shrink. You declare an invariant that the receiver shalt not grow or shrink the Vec. If B only reads and write, you're good. But if a future B breaks the invariant, bad things happen. As I said, specifically a bad idea; there's a much better type to use if the thing can't grow or shrink... No real world example, because I don't think we've run into memory safety issues with unsafe in the Rust code base I work in... but we only use unsafe where it's required (syscalls and other FFI).