Optional values

Optional type

pub fn Adjust(Value: i32) -> i32? {
    if Value < 0 {
        return none;
    }
    return Value + 1;
}

T? denotes an optional value. none represents absence. This example comes from the authored language acceptance fixtures.

Access and representation

Optionality is independent of reference or pointer access qualification. A writable access path cannot be created by wrapping or unwrapping an optional.

Handle absence deliberately

Pattern matching and version-specific optional operations distinguish a present value from absence. Do not assume a callable is nullable merely because it has an address at the machine level.