Unsafe blocks "contain the possible sources of unsafety" may be a more correct way to phrase it. It is better to know that only a specific subset of the codeba

Unsafe blocks "contain the possible sources of unsafety" may be a more correct way to phrase it. It is better to know that only a specific subset of the codebase could be responsible for memory unsafety even if that behavior may leak. If nothing else, it helps focus reviewing and testing effort.