References

A &T field accepts any value that structurally satisfies interface T. It's how a record or function declares "give me anything that looks like this" without committing to a specific concrete type.

Declaring a reference field

Use &InterfaceName as the field type. The accepted values are exactly those that satisfy the interface — every required field, with compatible types.

interface Drawable {
  x: f64
  y: f64
}

type Scene {
  focus: &Drawable     // any value with x and y of type f64
}

Why a reference?

A reference field lets a schema be open-ended without being untyped. A renderer that consumes &Drawable can accept any future shape that satisfies the contract — Circle, Image, Container, a user's Custom — without knowing what those concrete types are.

type Circle { x: f64  y: f64  radius: f64 }
type Square { x: f64  y: f64  side:   f64 }

s1 = Scene { focus: Circle { x: 0.0,  y: 0.0,  radius: 5.0 } }
s2 = Scene { focus: Square { x: 10.0, y: 10.0, side:   8.0 } }