Created attachment 28768 [details]
Code reproducing bug

Howdy,

I think this is a bug in G++. I have a call to a template function filter(T) in a template context. filter() is further overloaded before the instantiation point. G++ 4.6.1 and 4.5.2 (both under MinGW, sorry, I don't have access to a more recent version) seems to resolve it at declaration point (see attachment for the exact code reproducing bug):

namespace my
{
    ...
    // A function template that by default behaves as identity
    template <typename P>
    typename std::remove_reference<P>::type 
    filter(P&& p) throw() { return std::move(p); }
    ...
} // of namespace my 

// Since this is unrestricted template, ADL won't work, so we have to stick 
// this overloaded operator building an expression template into the global scope
template <typename P1>
inline auto operator&(P1&& p1) throw()
        -> typename std::enable_if<
                        my::is_mine<P1>::value,
                        my::address<decltype(my::filter(std::forward<P1>(p1)))>
                    >::type
{
    // NOTE: call to filter depends on template argument, thus have to be
    //       resolved at instantiation point. But it doesn't!
    return my::address<decltype(my::filter(std::forward<P1>(p1)))>
                               (my::filter(std::forward<P1>(p1)));
}

// We now declare few more classes modeling our concept: var and ref
namespace my
{
    template <typename T> class var;
    template <typename T> class ref;
    ...
    // and specialize function filter on them
    template <typename T> inline ref<var<T>>   filter( var<T>& t) throw() 
    { return ref<var<T>>(t); }
} // of namespace my 

int main()
{
    my::var<int> h;
    auto&& a = &h;  // Instantiate expression template via overloaded operator&
    std::cout << typeid(a).name() << std::endl;
}

GCC 4.6.1 output is:

    N2my7addressINS_3varIiEEEE

which indicates that there is no ref<> applied to var<> in instantiation of address<>. Visual C++ 10 and 11 produce:

    struct my::address<struct my::ref<struct my::var<int> > >

which have ref<> in between and is what I was actually expecting to have.

If I move the definition of overloaded operator& after the second namespace my is closed, the ref<> does properly appear on top of the var<>.

Can you please have a look at this?
Thank you!