Dynamically-dispatched type parameters

1 
if self.is_error {
     // below, CoRunnerBridge's types A, T, and C are constant w.r.t to this closure's container, but the 4th is unknown except for the fact that it implements Packet
     let actor = CoRunnerBridge::<A,T,C, dyn Packet>::new(self.get_and_increment_global_counter(), 
     self.vehicle_id, packet, ctx.address(), self.global_state_ptr.clone(), true);
     let _ = actor.start();
} else {
     // below, the type parameters in CoRunnerBridge are implicit within this closure's container
      let actor = CoRunnerBridge::new(self.get_and_increment_global_counter(), self.vehicle_id, packet, ctx.address(), self.global_state_ptr.clone(), false);
      let _ = actor.start();
}

I have an inbound packet type that can be one of many possible types. As seen on line 4, I customly set the 4th type parameter to by any type of Packet. Is this acceptable? If not, what is the next most idiomatic way to handle the situation?

2

If you want type inference to fill out the missing type, you can just use an underscore:

CoRunnerBridge::<A, T, C, _>::new(...

Otherwise if you truly want dyn Packet, i.e. the trait object, as the type, then it's fine to explicitly specify that.

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