module main

@[heap]
interface IGameObject {
mut:
    name  string
    speed f32
    owner ?&IGameObject
    collision(mut o IGameObject)
}

@[heap]
struct GameObject implements IGameObject {
mut:
    name  string
    speed f32
    owner ?&IGameObject
}

fn (mut gameobject GameObject) collision(mut o IGameObject) {
    _ = o
    if gameobject != gameobject.owner {
        eprintln('Collision')
    }
}

fn main() {
    mut ship := &GameObject{
        name: 'ship'
    }
    mut rocket := &GameObject{
        name:  'rocket'
        owner: ship
    }
    rocket.collision(mut ship)
}