Does the C++ standard allow using a typedef to rename a constructor?

Question

I was surprised to find that in VC++ 10, you can use a typedef to change the name of a class's constructor:

#include <iostream>

using namespace std;

class A
{
private:
    typedef A alias;

public:
    alias() { cout << "A ctor" << endl; }
};

int main()
{
    A(); // prints "A ctor"
    return 0;
}

Is this standard C++ or a Microsoft extension?

Answer 1

No; constructors do not have a name. You cannot take the address of a constructor or pass a function pointer around, or even just call it like a normal function. The syntax A::A() is just a special declarator syntax that allows you to declare and define the constructors, but it isn't a name.

That said, you cannot typedef objects (including function pointers) anyway, only types.

To comment on the MSVC behaviour, I quote from 12.1/3:

A typedef-name shall not be used [...] for a constructor declaration.