That looks similar to Rust's enums. The compiler enforces exhaustiveness in pattern matching. enum WebEvent { // An `enum` may either be `unit-like`,

That looks similar to Rust's enums. The compiler enforces exhaustiveness in pattern matching. enum WebEvent { // An `enum` may either be `unit-like`, PageLoad, PageUnload, // like tuple structs, KeyPress(char), Paste(String), // or like structures. Click { x: i64, y: i64 }, }