Macro sections 

macro_rules! sections {
    () => { ... };
    ($($section:ty),+ $(,)?) => { ... };
}

The sections a request reads, by type.

let app = Router::new()
    .route("/", get(handler))
    .layer(SnapshotLayer::new(sections![ServerConfig, FeaturesConfig]));

Each name expands to || Type::try_current(), which is what #[dynamic_config] generates. For a Dynamic<T> instance, call Sections::section with a closure instead.