#![cfg_attr(feature = "min_specialization", feature(min_specialization))] #![cfg_attr(feature = "downcast_unchecked", feature(downcast_unchecked))] #![cfg_attr(feature = "const_sort", feature(const_trait_impl, const_mut_refs))] #![feature(trait_upcasting)] #![allow(incomplete_features)] use std::any::Any; use trait_cast_rs::{make_trait_castable_decl, TraitcastableAny, TraitcastableAnyInfra}; struct HybridPet { name: String, } make_trait_castable_decl! { HybridPet => (Dog, Cat), // Multiple standalone entries in one macro invocation are possible. // HybridAnimal => (Cow, Cat), // Sunflower => (Flower, Plant) } impl HybridPet { fn greet(&self) { println!("{}: Hi", self.name) } } impl Dog for HybridPet { fn bark(&self) { println!("{}: Woof!", self.name); } } impl Cat for HybridPet { fn meow(&self) { println!("{}: Meow!", self.name); } } trait Dog { fn bark(&self); } trait Cat { fn meow(&self); } #[cfg_attr(test, test)] fn main() { // The box is technically not needed but kept for added realism let pet = Box::new(HybridPet { name: "Kokusnuss".to_string(), }); pet.greet(); let castable_pet: Box = pet; let as_dog: &dyn Dog = castable_pet.downcast_ref().unwrap(); as_dog.bark(); let as_cat: &dyn Cat = castable_pet.downcast_ref().unwrap(); as_cat.meow(); let any_pet: Box = castable_pet; let cast_back: &HybridPet = any_pet.downcast_ref().unwrap(); cast_back.greet(); }