I have recently tried to update my Zig project from 0.11.0 version of Zig, to 0.12.0. Zig compiler brings in its own build system. Since Zig is still under development, that API changes. The 0.12.0 changes forced me to dive a bit deeper into Zig’s source code. I went through Build.zig and Step.zig. What caught my attention was the usage of Tagged Unions. Tagged unions aren’t nothing new. C has them… kind of. In C, the tagged unions are more of a design pattern than a language feature.