explicit instantiation after specialization

Question

#include <iostream>
using namespace std;

template <typename>
  class Test
{
  void fun() { cout << "test" << endl; } 
  void bar() { cout << "bar"; }
};


template<>
  class Test<int>
{
  void fun(){}
};

template void Test<int>::fun();

I got an error:

error: template-id 'fun<>' for 'void Test::fun()' does not match any template declaration

But why?

I know it work if add template for fun in Test eg

template<>
  class Test<int>
{
  template <typename>
  void fun(){}
};

template void Test<int>::fun<bool>();

---

For function template

template<class T> void sort(Array<T>& v) { /*...*/ } // primary template

template<>  //explicit specialization of sort(Array<String>)
void sort<String>(Array<String>& v); // after implicit instantiation

template
void sort(Array<String>& v);// no matter before/after  void f(Array<String>& v) , it both works

void f(Array<String>& v) {
    sort(v); // implicitly instantiates sort(Array<String>&), 
}            // using the primary template for sort()

Answer 1

An explicit specialisation (that is, not a partial specialisation) is no longer a template. That means all of its members really exist (as if they were instantiated), so you cannot (and need not) instantiate them.