Both for sure, and which one is a bigger deal depends a lot on context. Cybersecurity issues make Rust a good choice for writing parsers for example. File form

Both for sure, and which one is a bigger deal depends a lot on context. Cybersecurity issues make Rust a good choice for writing parsers for example. File format parsers handle scary data from the internet (JPEG, X.509, etc), and those often contain addresses and offsets that turn into raw pointers in the implementation, so they're a common source of security bugs. At the same time, they're usually isolated behind a reasonably tight API, so it can be practical to rewrite them in Rust even when all the calling code is still C or C++ or even Python. On the other hand, fewer-mistakes-sucking-up-dev-time is an especially big deal in multithreaded code. There was a story from Mozilla about how they'd tried to add threading to part of Firefox (I think it might've been the CSS engine?) and failed multiple times, but then they succeeded in Rust. Threading bugs tend to be painful to reproduce, and Rust's compile-time checks are extremely valuable there.