I want to create c++ style's interrupt method, But doesn't work

Hi Guys:

I have sample class:

HEADER:

#ifndef __TEST__
#define __TEST__
#endif

#include <dos.h>

class Test {
   inline void interrupt handler(void) { /* do something */}
   void test();
};

CPP:

#include "Test.h"

void Test::test() {
   setvect(0, handler);
}

It won't compile:
Member function must be called or its address taken
Type mismatch in parameter '__handler' in call to 'setvect(int, void (interrupt *)(...))'


I got compiled successfully before but forgot exactly how and only remember using inline. If I change it like this:

HEADER:

#ifndef __TEST__
#define __TEST__
#endif

#include <dos.h>

class Test {
   void test();
};

CPP:
#include "Test.h"

void interrupt handler(void) { /* do something */}

void Test::test() {
   setvect(0, handler);
}

It compiles, the only difference is that interrupt function is not the member of class Test, and actual type doesn't change. Why I got this kind of errors?  I tried to find out how I did before but totally forgot? Thank you so much for help.

Anyway, what type does setvect function expect. It should expect "void (interrupt *)(...)" type but both ways do the same thing. I don't understand.