protected static TTo FromTReturn <TTo>(TReturn returnValue)
    {
#if NETCOREAPP3_1_OR_GREATER
        return(Unsafe.As <TReturn, TTo>(ref returnValue));
#else
        return(ContinuationsHelper.Convert <TReturn, TTo>(returnValue));
#endif
    }
    protected static TReturn ToTReturn <TFrom>(TFrom returnValue)
    {
#if NETCOREAPP3_1_OR_GREATER
        return(Unsafe.As <TFrom, TReturn>(ref returnValue));
#else
        return(ContinuationsHelper.Convert <TFrom, TReturn>(returnValue));
#endif
    }