I believe this was in the swift roadmap to have an opt-in borrow semantics for a block of code, if you want to do low level systems programming - just like rust

I believe this was in the swift roadmap to have an opt-in borrow semantics for a block of code, if you want to do low level systems programming - just like rust. But I guess it didn't fit to migrate from current obj-c ecosystem so they left it for later.