What does HackerNews think of evcxr?

Language: Rust

It does have a repl! https://github.com/evcxr/evcxr

Also, while cold compile times can be very slow of you have a lot of dependencies with macros etc, incremental compile time is often very fast. Rust has one of the most advanced incremental compilers out there. So for experimenting, tweaking and updating code, that's not going to have a long cycle.