#ifndef GSL_NARROW_H
#define GSL_NARROW_H
#include <gsl/gsl_assert> // for Expects
#include <gsl/gsl_util> // for narrow_cast
namespace gsl
{
struct narrowing_error : public std::exception
{
};

// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
template <class T, class U>
GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
constexpr
T narrow(U u) noexcept(false)
{
    constexpr const bool is_different_signedness = (std::is_signed<T>::value != std::is_signed<U>::value);

    const T t = narrow_cast<T>(u);

    if (static_cast<U>(t) != u
        || (is_different_signedness
            && ((t < T{}) != (u < U{}))))
    {
        throw narrowing_error{};
    }

    return t;
}
}
#endif // GSL_NARROW_H