Trait ChildPosition 

pub trait ChildPosition<Children, Child: Behavior>: ChildPosition { }

Static proof that Child occupies Position in a closed child sum.

This trait provides structural evidence only. It does not construct a choice, perform creation, or select a child through runtime inspection. A role cannot claim a position occupied by a different child:

struct CacheWorker;
struct QueueWorker;
struct Parent;
macro_rules! inert {
    ($actor:ty) => {
        impl behavior::Protocol for $actor {
            type Addr = behavior::MailAddr;
            type Msg = behavior::Never;
        }
        impl behavior::Behavior for $actor {
            type Protocol = Self;
            type Event = behavior::User<behavior::MailAddr, behavior::Never>;
            type Sends = Vec<behavior::Never>;
            type Ph = behavior::Never;
            type Error = behavior::Never;
            type Birth = behavior::NoBirths;
            fn transition(&mut self, _: behavior::ActiveTurn, event: Self::Event) -> behavior::BehaviorActed<Self> {
                match event.message {}
            }
        }
    };
}
inert!(CacheWorker);
inert!(QueueWorker);
impl behavior::Protocol for Parent {
    type Addr = behavior::MailAddr;
    type Msg = behavior::Never;
}
impl behavior::Behavior for Parent {
    type Protocol = Self;
    type Event = behavior::User<behavior::MailAddr, behavior::Never>;
    type Sends = Vec<behavior::Never>;
    type Ph = behavior::Never;
    type Error = behavior::Never;
    type Birth = behavior::Births<behavior::ChildChoice<QueueWorker, behavior::ChildChoice<CacheWorker, behavior::Never>>>;
    fn transition(&mut self, _: behavior::ActiveTurn, event: Self::Event) -> behavior::BehaviorActed<Self> {
        match event.message {}
    }
}
struct ForgedCacheRole;
impl behavior::ChildRole<Parent> for ForgedCacheRole {
    type Child = CacheWorker;
    type Position = behavior::ChildHead;
}

Implementors

impl<Child: Behavior> ChildPosition<Child, Child> for ChildHead

impl<Head, Tail, Position, Child> ChildPosition<ChildChoice<Head, Tail>, Child> for ChildTail<Position>

where Child: Behavior, Position: ChildPosition<Tail, Child>,

impl<Head: Behavior, Tail> ChildPosition<ChildChoice<Head, Tail>, Head> for ChildHead