Rapidcheck(C++) Arbitrary instance for `std::variant`

arbitrary-variant.hpp

// An Arbitrary instance generator for std::variant, for
// Rapidcheck: https://github.com/emil-e/rapidcheck

#include <variant>

namespace rc {
    
template<>
struct Arbitrary<std::monostate> {
    static Gen<std::monostate> arbitrary() {
        return gen::element(std::monostate());
    }   
};      
        
template <typename T, typename... Ts>
struct Arbitrary<std::variant<T, Ts...>> {
    static Gen<std::variant<T, Ts...>> arbitrary() {
        return gen::oneOf(
            gen::cast<std::variant<T, Ts...>>(gen::arbitrary<T>()),
            gen::cast<std::variant<T, Ts...>>(gen::arbitrary<Ts>())...);
    }
};      
        
} // namespace rc