There's at least one language, Koka (https://koka-lang.github.io/koka/doc/book.html https://koka-lang.github.io/koka/doc/book.html) that has effects in its type

There's at least one language, Koka (https://koka-lang.github.io/koka/doc/book.html https://koka-lang.github.io/koka/doc/book.html) that has effects in its type system. There are probably others. If you don't have effects, you could use union types.