Structs

struct Point {
    x i32
    y i32
}

func main() int {
    mut p := Point{x: 3, y: 4}
    p.x += 17
    return int(p.x + p.y)
}

Every field has to be given a value in a literal. There is no partial initialisation, because a half-built struct is a bug waiting for a reader.

The compiler is free to reorder fields to remove padding:

struct Task {
    done bool
    id   u64
    prio u8
}

Written in that order in C this is 24 bytes. Sword lays it out as id, done, prio and it comes to 16. If you need the declared order — because you are handing the struct to C — write extern struct.

A type can also be given a second name:

type Celsius = f64
type Point2 = Point

struct Point {
    x i32
    y i32
}

func warmer(t Celsius) Celsius {
    return t + 1.5
}

func main() int {
    p := Point2{x: 1, y: 2}
    reading f64 = 20.0
    return int(warmer(reading)) + int(p.x + p.y)
}

An alias is the type it names, not a new one: a plain f64 goes into warmer without a conversion, and Point2{...} is a Point. It is there to say what a type is for, or to avoid spelling out a long one. A type that is really new — one the compiler keeps apart from everything else — is a struct or an enum.