error C4716: must return a value, thrown by function that actually does return a value

My problem is quite simple, yet I fail to understand the cause of it and no similiar posting has turned up even after extensive research so here it is:

I have the following operator overload:

template <class T, size_t size>
    inline Vector<T, size> operator + (Vector<T, size> &a, Vector<T, size> &b) {
        Vector<T, size> result;
        for (auto i = 0; i < size; ++i) {
            result[i] = a[i] + b[i];
        }
        return result;
    }

Obiously there's only a single code path, and this path also returns a value, but compiling under Visual Studio 2013, I get an error C4716, stating that the function instantiated by the compiler 'must return a value'. I get this error for all instantiations I've tried so far. I also get this error for every other operator overload in the same header, all of which are structured similarly to the snippet above. Am I missing something obvious here?

EDIT: This is the templated vector class definition:

template <class T, size_t size>
    struct Vector {
        explicit Vector(T value = static_cast<T>(0)) {
            for (auto i = 0; i < size; ++i) {
                _data[i] = value;
            }
        }
        explicit Vector(const Vector &other) {
            for (auto i = 0; i < size; ++i) {
                _data[i] = other._data[i];
            }
        }
        explicit Vector(T values[size]) {
            for (auto i = 0; i < size; ++i) {
                _data[i] = values[i];
            }
        }
        T & operator = (const Vector &other) {
            for (auto i = 0; i < size; ++i) {
                _data[i] = other._data[i];
            }
            return *this;
        }

        T & operator [] (size_t index) {
            return _data[index];
        }

        T _data[size];
    };