template<typename T, std::size_t N>
constexpr std::size_t Length(const T(&)[N]) {
    return N;
}

struct Foo
{
    unsigned int temp1[3];
    void Bar()
    {
        unsigned int temp2[Length(temp1)]; // Error here
    }
};

error C2131: expression did not evaluate to a constant

note: failure was caused by a read of a variable outside its lifetime

note: see usage of 'this'