ALSchwalm

trait CloneMammal: Clone + Mammal{}

impl<T> CloneMammal for T where T: Clone + Mammal{}

ALSchwalm

let cat = Cat {
  meow_factor: 7
  purr_factor: 8
};

// No problem, a CloneMammal is impl for Cat
let clone_mammal: &CloneMammal = cat;

// Error!
let clone: &Clone = &clone_mammal;  

ALSchwalm

let cat = Cat {
  meow_factor: 7
  purr_factor: 8
};

let dog = Dog { ... };

let clone_mammal: &CloneMammal;
if get_random_bool() == true {
  clone_mammal = &cat;

ALSchwalm

ALSchwalm