Attribute Macro router_task 

#[router_task]

Apply to the RouterTask trait definition, an impl RouterTask<S [, K]> for T block, or — for less boilerplate — an inherent impl T { ... } block.

Use as #[cano::task::router].

Two surface forms on impl blocks:

1. Trait-impl form: #[task::router] impl RouterTask<S> for T { async fn route(..) { ... } } — user writes the trait header. The macro async-rewrites the RouterTask impl AND emits a companion impl Task<S> for T that delegates Task::run → RouterTask::route.
2. Inherent-impl form: #[task::router(state = S [, key = K])] impl T { async fn route(..) { ... } } — the macro builds the impl RouterTask<S [, K]> for T header from the attribute args, enforces that route is present (config / name may be overridden), and emits the same companion impl Task<S [, K]> for T.

On a trait definition (#[task::router] pub trait RouterTask ...) the macro just performs the async-fn-in-trait rewrite.

Because a blanket impl<R: RouterTask<..>> Task<..> for R would conflict (E0119) with the analogous blanket impls for the other specialized task traits — a type can implement more than one — the companion Task impl is generated per-use-site rather than as a blanket.