variadic class templates

Hi,

While experimenting with variadic templates, I tried something that
seems pretty simple, but works differently than I expected.  I made up
a problem: have a static member 'value' is true when the first two
template parameter types are the same, and false when they're not.
Only problem is, it always is false:

   #include <iostream>
   #include <ios>

   template <typename T, typename U, typename... Args>
     struct X
   {
     static const bool value = false;
   };

   template <typename T, typename... Args>
     struct X<T, T, ...Args>
   {
     static const bool value = true;
   };

   int main()
   {
     //
     // why doesn't this select the specialization?
     // (output is "false")
     //
     bool result = X<int, int>::value;
     std::cout << std::boolalpha << result << std::endl;
   }


Given partial specialization rules, I would have thought my
specialization was "more specialized" than the primary template, and
as such would be the template selected.  The same code, of course,
works as I expect when the trailing, unused variadic parameters are
removed.  Is there something about variadic templates that changes
the way they're selected, or is g++ not behaving correctly?
(I'm using g++ 4.3.1.)

Thanks,
Chris

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