The fish shell migrated to #Rust: https://github.com/fish-shell/fish-shell/pull/9512

Reasons:
- Nobody really likes C++ or CMake, and there's no clear path for getting off old toolchains. Every year the pain will get worse.
- C++ is becoming a legacy language and finding contributors in the future will become difficult, while Rust has an active and growing community.
- Rust is what we need to turn on concurrent function execution.
- Being written in Rust will help fish continue to be perceived as modern and relevant.