Type Alias ProducerBuildFn 

pub type ProducerBuildFn = Box<dyn Fn(ProducerCtx<'_>) + Send + Sync>;

Build closure type — the producer’s fn body, called once on first activation. The closure receives a ProducerCtx for setting up upstream subscriptions; emissions on the producer come from sink callbacks the closure registers.

Aliased Type

pub struct ProducerBuildFn(/* private fields */);