I came across union while looking through the code of the client's library for the new trading platform WATS by the Warsaw Stock Exchange (GPW), which currently is (still) under development. When I skimmed through the code, I noticed a lot of unsafe functions, that were the artifacts of using union s instead of struct ures or enum s. I never used or even encountered the unions before, so I wanted to learn about them. It proved to be an interesting journey, where I also revisited other Rust topics (like memory safety and ownership). According to official documentation , union uses the same syntax as structure. If I would describe it unofficially: it's like a child between struct and enum - it looks like structure, but behaves more like enum - but is neither of them.…