That's all interesting about const fns, but AFAIK any dependency can add a build.rs that executes anything - and is usually automatically executed by the langua

That's all interesting about const fns, but AFAIK any dependency can add a build.rs that executes anything - and is usually automatically executed by the language server doing a build on Cargo.toml file change. Not a Rust-only problem, but one that people should be aware of in general.