Structs, enums, methods

Structs

Plain records. Fields are laid out in declaration order, addressed by name in source.

▸ live snippet open in playground →

Methods

The receiver goes between function and the name. Calls dispatch by receiver type at the call site.

▸ live snippet open in playground →

Enums

Tagged unions with optional positional payloads. The standard library injects Option[T] and Result[T, E], so you don’t re-declare them.

▸ live snippet open in playground →

Match is exhaustive

The checker fails the build if a match misses a variant, unless a wildcard _ arm acknowledges the gap.

function describe(s: Shape): string {
    match (s) {
        Circle(_) => { return "round"; },
        // error: missing variant Rectangle
        //        ^~~~~
    }
}

Next: Modules →