As a member of the development team for a C static analyzer, I use OCaml, which is also my favorite programming language, but that is because I'm from the generation in which it was the new thing (I learnt it when it had the same level of maturity as Rust, at a time when Rust didn't exist). It helps that it's perfect for writing compilers and static analyzers.

There are a lot of problems that seem a good match for Rust, and Rust is first in my list of programming languages I will never find the time to learn but wish I could.

Why won't you ever find time? It should only take a good 20 hours of reading and playing with code before you start to grok it.

I spent the early part of my career bragging about how many programming languages I knew, and the later part of my career complaining about how I don't know any of them well enough.

I certainly wouldn't go for quantity there, but if you really want to learn Rust you should. It brings some groundbreaking new ideas to programming and is more than "just another language".