Function narrow_cast

Fleece/Support/NumConversion.hh:66–105

    #if DEBUG
        template<typename Out, typename In>
        static Out narrow_cast (In val) {
            static_assert(::std::is_arithmetic<In>::value && ::std::is_arithmetic<Out>::value, "Only numeric types are valid for narrow_cast");
            if(sizeof(In) <= sizeof(Out) && ::std::is_signed<In>::value == ::std::is_signed<Out>::value) {
                return (Out)val;
            }

            // Comparing an unsigned number against a signed minimum causes issues, at least on Windows,
            // but if the output is signed and the input is unsigned then there is never a case where
            // the input could underflow the output.  The reverse situation does not appear to be true.
            // the input could underflow the output.  The reverse situation does not appear to be true.
            bool min_ok = std::is_signed<Out>::value && !std::is_signed<In>::value;

#ifdef Assert
            if(::std::is_floating_point<In>::value) {
                Assert(val >= std::numeric_limits<Out>::min() && val <= ::std::numeric_limits<Out>::max(), 
                    "Invalid narrow_cast %g -> %s", (double)val, typeid(Out).name());
            } else if(::std::is_signed<In>::value) {
                Assert((min_ok || val >= std::numeric_limits<Out>::min()) && val <= ::std::numeric_limits<Out>::max(), 
                    "Invalid narrow_cast %" PRIi64 " -> %s", (int64_t)val, typeid(Out).name());
            } else {
                Assert((min_ok || val >= std::numeric_limits<Out>::min()) && val <= ::std::numeric_limits<Out>::max(), 
                    "Invalid narrow_cast %" PRIu64 " -> %s", (uint64_t)val, typeid(Out).name());
            }
#else
            char message[256];
            if(::std::is_floating_point<In>::value) {
                sprintf(message, "Invalid narrow_cast %g -> %s", (double)val, typeid(Out).name());
                throwIf(val < std::numeric_limits<Out>::min() || val > std::numeric_limits<Out>::max(), InternalError, message);
            } else if(::std::is_signed<In>::value) {
                sprintf(message, "Invalid narrow_cast %" PRIi64 " -> %s", (int64_t)val, typeid(Out).name());
                throwIf((!min_ok && val < std::numeric_limits<Out>::min()) || val > std::numeric_limits<Out>::max(),
                    InternalError, message);
            } else {
                sprintf(message, "Invalid narrow_cast %" PRIu64 " -> %s", (uint64_t)val, typeid(Out).name());
                throwIf((!min_ok && val < std::numeric_limits<Out>::min()) || val > std::numeric_limits<Out>::max(),
                    InternalError, message);
            }
#endif
            return (Out)val;
        }
    #else
        template<typename Out, typename In>
        static inline Out narrow_cast(In val) {