Module dispatch_tag 

Phase 216.A.4 — tag types Node authors hold on Self::State to match against incoming Callback in ExecutableNode::on_callback.

Each tag is an opaque newtype around a &'static str (the stable callback identifier shape — see CallbackId). The three flavors (SubscriptionTag, ServiceTag, ActionTag) keep the kind distinct at the type level so a Node author can’t accidentally match a subscription tag against a service callback.

Tag types support:

• Into<CallbackId<'static>> — convert a tag into a borrowable CallbackId when handing off to the runtime.

• PartialEq<Callback<'_>> — match directly against the Callback delivered to ExecutableNode::on_callback:

  if state.sub_chatter == cb { /* … */ }

• placeholder — const-fn sentinel used by macro-emitted init() bodies before the real tag is resolved (the macro overwrites at register time).

The companion NodeContext::create_subscription_static / _service_static / _action_static methods that consume these tags at register time land in a follow-up commit; this commit ships only the types so the 216.B.5 + 216.C.5 example carving can declare them.

Structs

ActionTag

Tag identifying an action-server callback registered on a Node.

ServiceTag

Tag identifying a service-server callback registered on a Node.

SubscriptionTag

Tag identifying a subscription callback registered on a Node.