#pragma once

#include "tl/detail/prologue.h"
#include "tl/plain_crash.h"
#include "tl/type_traits.h"

namespace tl
{

namespace detail
{

template <class T, class U>
struct is_same_signedness : integral_constant<bool, is_signed<T>::value == is_signed<U>::value>
{
};

}

template <class T, class U>
T narrow(U u) noexcept
{
    T t = static_cast<T>(u);
    if (static_cast<U>(t) != u)
        TL_PLAIN_CRASH("Narrowing error");
    if (!detail::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
        TL_PLAIN_CRASH("Narrowing error");
    return t;
}

}