2catycm

#include <array>
#include <type_traits>

template<typename F>
auto foo(F f) -> typename std::enable_if<
    std::is_same<decltype(f(std::declval<int>(), std::declval<int>())), std::array<int, 2>>::value,
    std::array<int, 2>
>::type
{
    return f(1, 2);

2catycm

use validator::Validate;
impl<T: Validate> Validate for swagger::Nullable<T> {
    fn validate(&self) -> Result<(), validator::ValidationErrors> {
        match self {
            swagger::Nullable::Value(v) => v.validate(),
            swagger::Nullable::Null => Ok(()),
        }
    }
}