rip.cpp

// No errors
template <typename Container>
std::size_t size_in_bytes(Container& c)
{
    return c.size() * sizeof(typename Container::value_type);
}

//Error	C2065	'value_type': undeclared identifier
//Error	C2825	'Container': must be a class or namespace when followed by '::'	
//Error	C2510	'Container': left of '::' must be a class/struct/union
template <typename Container>
std::size_t size_in_bytes(Container&& c)
{
    return c.size() * sizeof(typename Container::value_type); // <-- from this line (obv)
}