Visual Studio 2012中的奇怪错误

Question

why does this code compiles and run on visual studio 2012? is this just a bug or i missing something

namespace SSSS
    {
        namespace SSS
        {
            template <class T>
            class SS
            {
            public:
                typedef T ValueType;
                SS(){std::cout<<T();}
                SS(T t) { std::cout<<t;}
            };

            typedef SS<double> DD;
        }
    }
    int main()
    {
        SSSS::SSS::DD::SS d;
    }

Answer 1

It sounds like your compiler is interpreting SS as the injected class name; in which case, it is a type, so the declaration is valid.

However, the name lookup rules say that it should instead be interpreted as the constructor, not the class, so your compiler is wrong. Others reject the code: http://ideone.com/7fJ1VM

Valid type names would be the type alias DD , or an elaborated type specifier using the injected class name, class DD::SS .