Overload resolution bug repro in VS2015 RTM (gathered from Stephan T. Lavavej aka STL)

overload_resolution.bug.cpp

// Discussion: https://github.com/Snaipe/Criterion/issues/51

namespace Std {
    template <class Elem> struct CharTraits { };

    template <class Elem, class Traits = CharTraits<Elem>> struct BasicOstream {
        void operator<<(const void *) = delete;
    };

    template <class Traits> void operator<<(BasicOstream<char, Traits>&, const char *) = delete;
}

template <typename CharT> struct MyOstream : Std::BasicOstream<char> { };

MyOstream<char> * stream;

#ifdef AVOID_TEMPLATE
    MyOstream<char>& call() {
#else
    template <typename RandomT = double> MyOstream<char>& call() {
#endif
    stream = new MyOstream<char>();
    return *stream;
}

int main() {
    MyOstream<char>& f = call();
    f << "Foo";
}