Contracts are about specifying static properties of the system, not dynamic properties. Features like assert /check/ (if enabled) static properties, at runtime. static_assert comes closer, but it’s still an awkward way of expressing Hoare triples; and the main property I’m looking for is the ability to easily extract and consider Hoare triples from build-time tooling. There are hacky ways to do this today, but they’re not unique hacky ways, so they don’t compose across different tools and across code written to different hacks.