Member function template of class template can't find definition despite explicit instantiation present. Doesn't link

Question

Edit: This is not a duplicate of the linked question since I am using explicit instantiation and only a specific type of member functions do not link (others do

Answer 1

You should use the explicit instantion of the method template<typename T> template<typename U> Vector<T> Vector<T>::operator+(const Vector<U> & other) const (for all possible pairs of T and U) in addition to the explicit instantion of the Vector<T> class:

template Vector<int> Vector<int>::operator+(const Vector<short> & other) const;

Also you may simply move the definition of the Vector<T>::operator+ method to the header file.

In C++11 the extern template directive was introduced. You may use it in the header file for Vector<T> class (as @StoryTeller suggested in the comments):

extern template struct Vector<int>;

...to prevent the compiler from instantiating the Vector<T> class in every translation unit its specializations are used. Of course the same extern template directives may also be used for all Vector<T>::operator+ specializations explicitly instantiated in the .cpp file.