nullptr placeholder without #define

Hi all,

I'm a little alergic to #define so when I wanted to make myself a
placeholder
for nullptr keyword for C++0x compability I came up with something
like this:

     const struct nullptr_t {
         template<class T>
         operator T*() const { return 0; }
         template<class T, class U>
         operator T U::*() const { return 0; }
     } nullptr = {};

     template<class T>
     bool operator==(T* lhs, const nullptr_t rhs) { return lhs == 0; }

     template<class T>
     bool operator==(const nullptr_t lhs, T* rhs) { return rhs == 0; }

     template<class T, class U>
     bool operator==(T U::* lhs, const nullptr_t rhs) { return lhs ==
0; }

     template<class T, class U>
     bool operator==(const nullptr_t lhs, T U::* rhs) { return rhs ==
0; }

It does not pass only one from Basic Cases from n2431:

     if( nullptr == 0 ); // error

On GCC 4.3.3 it compiles.
On MinGW-GCC 3.4.5 it crushes the compiler.

I didn't do tests for other compilers nor Advanced Cases from n2431.

Ofcourse while reading n2431 for tests I've found that this is
proposed alternate solution (library implementation instead of
keyword).

Nevertheless I thought that it could interest people as alergic go
#define as I am and who didn't read said C++0x proposal.

Cheers
Sfider

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