To declare a conversion function which has the pointer-to-function return type

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We can declare such an operator function via typedef declaration as follows:

#include <iostream>

typedef int (*int_ptr)(int, int) ;

struct A
{
private:
    int (*_foo)(int a, int b);

public:
    operator int_ptr()
    {
        return _foo;
    }
};

int main(){ }

and it works as I was supposed. But is it possible to do that without the typedef declaration? I mean to embed a pointer to function declarator into an operator function declaration. I tried

operator (int *())()
operator (int (*)())()
operator int (*)()()

It didn't work. But, when I tried to use:

operator int *()()

DEMO

Clang prints the following error:

error: must use a typedef to declare a conversion to 'int *()'

So, such declarators explcitly forbidden by the Standard, don't they? If so, couldn't you get a reference?

asked 1 min ago

Dmitry Fucintv

3,736

To declare a conversion function which has the pointer-to-function return type