Valid C++, or not?

Hi all,

The code below fails to compile with GCC 4.1 and higher. GCC 4.2.1
produces the following error:
   error: no match for 'operator<<' in 'std::cout <<
KeyValue::getVecBool() const()'

Somehow, the compiler fails to find the conversion of vector<bool> to
KeyValue. Older GCC compilers don't have any problems with this code.
So the question is:
   Is this valid C++ (and hence a compiler bug), or is it not.?

BTW: GCC 4.2.1 will happily compile the code, when I make the friend
ostream& operator<<() global.

<code>
#include <iostream>
#include <map>
#include <string>
#include <vector>

using namespace std;

struct KeyValue
{
   KeyValue() {}
   KeyValue(bool) {}
   KeyValue(const vector<bool>&) {}
   vector<bool> getVecBool() const { return vector<bool>(); }
   friend ostream& operator<<(ostream& os, const KeyValue&) { return
os; }
};

int main()
{
   map<string, KeyValue> par;
   par["b1"] = true;
   cout << par["b1"].getVecBool() << endl;
}
</code>

--
      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]