Class container

tests/DeductionGuideTest.cpp:8–11

namespace Test {
// declaration of the template
template<class T> struct container {
    container(T t) {}
    template<class Iter> container(Iter beg, Iter end);
};
// additional deduction guide
template<class Iter>
container(Iter b, Iter e) -> container<typename std::iterator_traits<Iter>::value_type>;