> This is a case of the Rust community overselling a minor feature as a game-changing novelty. Sum types reify control flow into an object from which said cont

> This is a case of the Rust community overselling a minor feature as a game-changing novelty. Sum types reify control flow into an object from which said control flow can be retrieved. Compiler checked sum types remove the possibility of retrieving inconsistent control flow. The transform is equivalent to callback to future. It's one of the things that looks unimportant until you use it. After that, the absence is repeatedly experienced when working with C++. We don't use tagged unions much because the ergonomics are terrible.