Pattern matching

type IncomingMessage =
    | CounterIncBy
    | CounterReset
    // ...

// ... after parsing a message
match (msg) {
    CounterIncBy => {
        newCounter = curCounter + msg.byValue
    }
    CounterReset => {
        newCounter = 0
    }
    // ...
}

fun processValue(value: int | slice) {
    match (value) {
        int => {
            value * 2
        }
        slice => {
            value.loadUint(8)
        }
    }
}

fun errDemo(v: int | slice | Point) {
    match (v) {
        slice => { v.loadAddress() }
        int => { v * 2 }
        // error: missing `Point`
    }
}

type Pair2 = (int, int)
type Pair3 = (int, int, int)

fun getLast(tensor: Pair2 | Pair3) {
    return match (tensor) {
        Pair2 => tensor.1,
        Pair3 => tensor.2,
    }
}

fun getPair2Or3(): Pair2 | Pair3 {
    // ...
}

fun demo() {
    match (val v = getPair2Or3()) {
        Pair2 => return v.0 + v.1,
        Pair3 => throw v.0 + v.1 + v.2,
    }
}

val nextValue = match (curValue) {
    1 => 0,
    0 => 1,
    else => -1
};

// statement form
match (curValue) {
    1 => { nextValue = 0 }
    0 => { nextValue = 1 }
    -1 => throw NEGATIVE_NOT_ALLOWED
}

// expression form, `else` required
val nextValue = match (curValue) {
    // ...
    else => 1 + 2
}

match (someColor) {
    Color.Red => {}
    Color.Green => {}
    // error: Color.Blue is missing
}

match (someColor) {
    Color.Red => {}
    else => {}
}