This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 110b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2023-01-15


602. When is the injected-class-name of a class template a template?

Section: 13.8.2  [temp.local]     Status: C++11     Submitter: Daveed Vandevoorde     Date: 23 October 2006

[Voted into the WP at the March, 2011 meeting as part of paper N3262.]

Consider the following example:

    template<class T>
    struct A {
         template<class U>
             friend struct A; // Which A?
    };

Presumably the lookup for A in the friend declaration finds the injected-class-name of the template. However, according to 13.8.2 [temp.local] paragraph 1,

The injected-class-name can be used with or without a template-argument-list. When it is used without a template-argument-list, it is equivalent to the injected-class-name followed by the template-parameters of the class template enclosed in <>. When it is used with a template-argument-list, it refers to the specified class template specialization, which could be the current specialization or another specialization.

If that rule applies, then this example is ill-formed (because you can't have a template-argument-list in a class template declaration that is not a partial specialization).

Mike Miller: The injected-class-name has a dual nature, as described in 13.8.2 [temp.local], acting as either a template name or a class name, depending on the context; a template argument list forces the name to be interpreted as a template. It seems reasonable that in this example the injected-class-name has to be understood as referring to the class template; a template header is at least as strong a contextual indicator as a template argument list. However, the current wording doesn't say that.

(See also issue 1004.)

Proposed resolution (November, 2010) [SUPERSEDED]:

This issue is resolved by the resolution of issue 1004.