Syntax to befriend one constructor of template type T

  c++, c++11, c++14, templates

Making a constructor friend is possible in C++:

class A {
    A() { B b; }
    class B {
        friend A::A();

How can I achieve the same but with a template class:

template< typename T >
class EnforceOnlyOneIntConstructor
    EnforceOnlyOneIntConstructor() {}
    //friend T::T(int);
    //friend T::OnlyOneIntConstructor(int);
    friend void T::regularFun(int);

class OnlyOneIntConstructor
    //EnforceOnlyOneIntConstructor< OnlyOneIntConstructor > m_trick;
    OnlyOneIntConstructor(int) //: m_trick{}

    void regularFun(int) {
        EnforceOnlyOneIntConstructor< OnlyOneIntConstructor > m_trick;


int main() {
    OnlyOneIntConstructor a(10);

I don’t know if it is even possible. Without commenting out the problematic sections the compiler gives an error:
error: C++ requires a type specifier for all declarations

Source: Windows Questions C++