Re: Template conversion operator ambiguity?

While "porting" some existing code to g++, I ran into a problem with a
generic value class that uses a template conversion operator to return
values. Here's a stripped down version:

#include <string>

struct Value
{
   Value() {}

   template <typename T> operator T() { return T(); }

};

int main()
{
   Value v;

   int n(v);
   std::string s(v);

}

My original compiler is happy with the string initialisation, but g++
whinges about the conversion being ambiguous (edited to cut the noise):

example.cc:15: error: call of overloaded 'basic_string(Value&)' is ambigu=

candidates are:
std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*,
const _Alloc&)

std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const
std::basic_string<_CharT, _Traits, _Alloc>&)

std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _Alloc&)

But it will happily accept

std::string s = v;

So my question is, which compiler is correct?