Templates and overloading problem

Hi All,
I was wondering if someone can give me assistance with the following
small program. There are two sections controlled by an #if. The
first section compiles and runs correctly (using g++), the alternative
section errors out. Both sections are attempting to do the same
thing. There is a class with a static member (wrapper) which is
overloaded based on a function template type (i.e. R func()).

I can't understand why the second section errors out. It seems like
the enable_if should be able to overload the member function types
within the same class definition.

Any help, explanations would be appreciated.

Thanks,
Oz

PS. I've provided is_void and enable_if_c which are basically like
boost's but allow simple standalone compilation of this program with
any C++ compiler.

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <iostream>

// is_void type trait
template <typename T> struct is_void { static const bool value =
false; };
template <> struct is_void<void> { static const bool value = true; };

// enable_if_c like boost
template <bool b, typename T> struct enable_if_c {};
template <typename T> struct enable_if_c<true, T> { typedef T type; };

// some simple functions
void foo() { std::cout << "foo\n"; }
int bar() { std::cout << "bar\n"; return 42; }

#if 1

// this works

template <typename R, typename enable = void> struct obj;

template <typename R>
struct obj<R, typename enable_if_c<is_void<R>::value, void>::type>
{
   template <R func()> static void wrapper() { func(); }
};

template <typename R>
struct obj<R, typename enable_if_c<!is_void<R>::value, void>::type>
{
   template <R func()> static void wrapper()
   {
     std::cout << "non-void: " << func() << std::endl;
   }
};

#else

// this doesn't work

template <typename R>
struct obj {
   template <R func()>
   static typename enable_if_c<is_void<R>::value, void>::type wrapper()
   {
     func();
   }

   template <R func()>
   static typename enable_if_c<!is_void<R>::value, void>::type wrapper
()
   {
     std::cout << "non-void: " << func() << std::endl;
   }
};

#endif

int main()
{
   obj<void>::wrapper<foo>();
   obj<int>::wrapper<bar>();
   return 0;
}

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