alt Hacker News> There's a formal proof asserting that if you keep up the safety invariants within an unsafe region then that will not infect other code, even in the presence of arbitrary other correctly-written unsafe blocks.
In general "unsafe" does not compose.
"if you keep up the safety invariants within an unsafe region"
This condition is doing a lot of heavy lifting.
Here's an article about the research on it which lays out the properties in simple terms: https://smallcultfollowing.com/babysteps/blog/2016/10/02/obs...
I'm curious why you think that statement is doing heavy lifting. It's much easier to write and verify that a few lines of code are correct than it is to write and verify that an entire program is correct. But that's the norm in C and Zig, and historically people haven't been very good at it. That's why we try to do it as little as possible.