Try preventing static casts when calling hash_value.

[SVN r63716]

include/boost/functional/hash/hash.hpp

@@ -15,6 +15,7 @@
 #include <boost/functional/hash/detail/hash_float.hpp>
 #include <string>
 #include <boost/limits.hpp>
+#include <boost/static_assert.hpp>
 
 #if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
 #include <boost/type_traits/is_pointer.hpp>
@@ -29,6 +30,14 @@
 
 namespace boost
 {
+    // If you get a static assertion here, it's because hash_value
+    // isn't declared for your type.
+    template <typename T>
+    std::size_t hash_value(T const&) {
+        BOOST_STATIC_ASSERT((T*) 0 && false);
+        return 0;
+    }
+
     std::size_t hash_value(bool);
     std::size_t hash_value(char);
     std::size_t hash_value(unsigned char);

test/Jamfile.v2

@@ -50,6 +50,8 @@ test-suite functional/hash
         [ run container_no_fwd_test.cpp ]
         [ compile-fail hash_no_ext_fail_test.cpp ]
         [ compile-fail namespace_fail_test.cpp ]
+        [ compile-fail implicit_fail_test.cpp ]
+        [ compile-fail shared_ptr_fail_test.cpp ]
         [ run hash_no_ext_macro_1.cpp ]
         [ run hash_no_ext_macro_2.cpp ]
     ;

test/implicit_fail_test.cpp

@@ -0,0 +1,16 @@
+#include <boost/functional/hash.hpp>
+
+namespace test
+{
+    struct base {};
+    std::size_t hash_value(base const&) { return 0; }
+    
+    struct converts { operator base() const { return base(); } };
+}
+
+int main() {
+    boost::hash<test::converts> hash;
+    test::converts x;
+    
+    hash(x);
+}

test/shared_ptr_fail_test.cpp

@@ -0,0 +1,11 @@
+#include <boost/functional/hash.hpp>
+#include <boost/shared_ptr.hpp>
+
+// This should obviously pass if shared_ptr ever supports Boost.Hash.
+
+int main() {
+    boost::hash<boost::shared_ptr<int> > hash;
+    boost::shared_ptr<int> x(new int(10));
+    
+    hash(x);
+}