interface IEdible
{
    public func eat(): void;
}

template < T >
if (IsDerivedOf< T, IEdible >)
struct FoodBox
{
    var food: T[];
}

class Carrot: IEdible
{
    public override func eat(): void {}
}

class Car {}

func main(): void
{
    var carrotBox: FoodBox< Carrot >;   // OK

    // var carBox: FoodBox< Car >;      // Not allowed
    static assert( not trait(compiles, func() { var carBox: FoodBox< Car >; } ));
}