Why is no empty argument list required inside this class definition?

Question

When instantiating a variable that has the type of a templated class using only the standard type arguments, the syntax looks like this:

template<typename Arg = int>
class Templ;

Templ<>& myTempl;

Leaving out the empty argument list <> should give a compile error because a template argument list is needed.

But apparently (at least under VS2013), the following declaration does not need a template argument list:

template<typename Arg> //" = int" left out
class Templ{
    Templ& myTempl; //no <> here
};

But why does this work? According to IntelliSense, the correct type (Templ<int>) is selected by the compiler, so it works as intended, but shouldn't the member declaration still require an empty argument list?

EDIT: No, it doesn't work as intended. I didn't check it thoroughly enough. When hovering over the line Templ<short>::myTempl, IntelliSense reveals its type to be short.

Answer 1

The class name is injected into the class scope

9 Classes [class]

2 A class-name is inserted into the scope in which it is declared immediately after the class-name is seen. The class-name is also inserted into the scope of the class itself; this is known as the injected-class-name. For purposes of access checking, the injected-class-name is treated as if it were a public member name. A class-specifier is commonly referred to as a class definition. A class is considered defined after the closing brace of its class-specifier has been seen even though its member functions are in general not yet defined. The optional attribute-specifier-seq appertains to the class; the attributes in the attribute-specifier-seq are thereafter considered attributes of the class whenever it is named.

and similarly for class templates

14.6.1 Locally declared names [temp.local]

1 Like normal (non-template) classes, class templates have an injected-class-name (Clause 9). The injectedclass- name can be used as a template-name or a type-name. When it is used with a template-argument-list, as a template-argument for a template template-parameter, or as the final identifier in the elaborated-typespecifier of a friend class template declaration, it refers to the class template itself. Otherwise, it is equivalent to the template-name followed by the template-parameters of the class template enclosed in <>.

so that you can use Templ where you mean Templ<Arg>.

Answer 2

This is called the injected class name.

Inside a class template, the name of the template without any template argument list refers to the current instantiation, so Templ means Templ<Arg> (and not Templ<> which is Templ<int> and so not necessarily the same).