I mentioned it elsewhere here but I think the Terra research language has explored this area more thoroughly than Rust, just because that its only purpose. The website and academic papers are definitely worth a skim: terralang.org

It’s basically a powerful LLVM-based compilation library exposed where everything is exposed through Lua bindings. The default Terra compiler is just a Lua script that you can pull apart, extend, rearrange, etc. It’s all designed for ease of experimentation, whereas Rust has to worry about being a rock-solid production compiler.