Toward a better list iterator for the kernel

In Rust, variable name re-use is actually rather idiomatic. I used to be skeptical about it, as my experience also was of confusing bugs, or at least code. However, I've embraced this idiom in Rust for purely pragmatic reasons:

In C, your 'char* str' variable will be the same type before and after your null check, but in Rust those are two separate types. A given "content" can undergo multiple type changes in as many lines as the assumptions are checked, it'd be really tedious to have to come up with new names for essentially the same content.

You can find an example of shadowing in the Rust Book in the second chapter! https://doc.rust-lang.org/book/ch02-00-guessing-game-tuto... (the 'guess' name is reused as we go from the raw input string to the actual integer)