I think the Rust approach is incorrect - if the runtime behavior can change based on the machine that the code gets run on, why is it so important the build time behavior has such a restrictive definition? Especially considering build.rs can be used to bypass that definition anyway. It feels like a weird cut to make that I can’t figure out the understanding for. It feels like it inherited the const philosophy of c++11 without reexamining if it’s actually a good idea.