This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

2874. Qualified declarations of partial specializations

[Accepted as a DR at the June, 2024 meeting.]

(From submission #521.)

Consider:

  namespace N {
    template<typename T>
    struct A;
  }

  template<>
  struct N::A<int>;     // OK

  template<typename T>
  struct N::A<T*>;      // error: invalid use of elaborated-type-specifier with a qualified-id

However, all major implementations support this.

Proposed resolution (approved by CWG 2024-05-17):

Change in 9.2.9.5 [dcl.type.elab] paragraph 2 as follows:

If an elaborated-type-specifier is the sole constituent of a declaration, the declaration is ill-formed unless it is an explicit specialization (13.9.4 [temp.expl.spec]), a partial specialization (13.7.6 [temp.spec.partial]), an explicit instantiation (13.9.3 [temp.explicit]), or it has one of the following forms:

  class-key attribute-specifier-seqopt identifier ;
  class-key attribute-specifier-seqopt simple-template-id ;

In the first case, the elaborated-type-specifier declares the identifier as a class-name. The second case shall appear only in an explicit-specialization (13.9.4 [temp.expl.spec]) or in a template-declaration (where it declares a partial specialization (13.7 [temp.decls]). The attribute-specifier-seq, if any, appertains to the class or template being declared.