Re: ADL

Hello all,

Sometimes I experience strange issue with the ADL (VS9.0 SP1):

// struct.hpp
namespace A
{
 namespace B
 {
   struct Struct {};
   std::ostream &operator<< (std::ostream &os, const Struct &s);
 }
}
//.....
// outputter.hpp
namespace A
{
 template<class T> class Outputter
 {
   //...
   void f()
   {
     B::Struct s;
     std::cout << s;
   }
 };

At some other place, where template Outputter is instantiated, I've
got the compiler error:

error C2679: binary '<<' : no operator found which takes a
right-hand operand of type 'A::B::Struct' (or there is no
acceptable conversion)

I would think that the operator is really undeclared yet at the
point of the template instantiation, but:
1) it's declared just after A::B::Struct, so if the compiler does
see Struct it should see operator << as well
2) next error lines state:

2> c:\program files\microsoft visual studio 9.0\vc\include
\ostream(653): could be 'std::basic_ostream<_Elem,_Traits>
&std::operator <<<wchar_t,std::char_traits<wchar_t>>
(std::basic_ostream<_Elem,_Traits> &,const char *)' [found using
argument-dependent lookup]
2> with
2> [
2> _Elem=wchar_t,
2> _Traits=std::char_traits<wchar_t>
2> ]
2> c:\program files\microsoft visual studio 9.0\vc\include
\ostream(700): or 'std::basic_ostream<_Elem,_Traits>
&std::operator <<<wchar_t,std::char_traits<wchar_t>>
(std::basic_ostream<_Elem,_Traits> &,char)' [found using argument-
dependent lookup]
2> with
2> [
2> _Elem=wchar_t,
2> _Traits=std::char_traits<wchar_t>
2> ]
2> d:\myproject\struct.hpp(471): or 'std::ostream
&A::B::operator <<(std::ostream &,const A::B::Struct &)' [found
using argument-dependent lookup]

So the right declaration is found! Why isn't it used?