That's surprising. I would've thought most C programmers have at least some experience writing C++, and C++ programmers (and C programmers too, but I don't know anyone who programs primarily in C so I can't comment) already do many of the things Rust does for you. Like thinking about lifetimes, const by default, moving instead of copying, avoiding raw pointers like the plague, etc.
Someone who has never thought about that stuff must surely find it harder to appreciate Rust.
