> I think we have a terminology mixup. Not really -- my core point was that C++ compilation units are usually smaller than Rust. Most C++ codebases I've dealt

> I think we have a terminology mixup. Not really -- my core point was that C++ compilation units are usually smaller than Rust. Most C++ codebases I've dealt with will be of the kind where there's a single stage where all the cpp files get compiled one by one. Not a step by step process where one "module" gets compiled followed by its dependencies. For these codebases, you have a huge win if you can touch a header file and only cause a small set of things to be recompiled. For Rust codebases, it's already a large compilation unit, so you're usually already paying that cost (and with incremental compilation the compiler can reduce that cost, but smartly, so you get a sweet spot where you're not compiling too much but are not missing anything either). But yes, being able to skip compilation of downstream crates would be nice. (You're right that a crate is compiled into a .exe or .so or whatever) > Pardon my Rust ignorance, but is this scenario significantly different from C++ templates? The layout of a (judiciously) templated C++ class may not be "immediately obvious" but in practice it's often still very straightforward to infer. ADTs are tagged unions. There's a tag, but it can sometimes be optimized out and hidden away elsewhere. You can mentally unravel templates to figure them out. Enums are a whole new kind of layout that you need to understand.