add defaulted parameter for function_requires() to work around problems

with Compaq C++ and MSVC


[SVN r13040]

include/boost/concept_check.hpp

@@ -19,6 +19,8 @@
 #include <utility>
 #include <boost/type_traits/conversion_traits.hpp>
 #include <boost/static_assert.hpp>
+#include <boost/type.hpp>
+
 
 #if defined(BOOST_MSVC) || defined(__BORLANDC__)
 #define BOOST_FPTR
@@ -36,8 +38,9 @@ namespace boost {
 
 template <class T> inline void ignore_unused_variable_warning(const T&) { }
 
+// the unused, defaulted parameter is a workaround for MSVC and Compaq C++
 template <class Concept>
-inline void function_requires()
+inline void function_requires(type<Concept>* = 0)
 {
 #if !defined(NDEBUG)
   void (Concept::*x)() = BOOST_FPTR Concept::constraints;