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

635. Names of constructors and destructors of templates

There is a discrepancy between the syntaxes allowed for defining a constructor and a destructor of a class template. For example:

    template <class> struct S { S(); ~S (); };
    template <class T> S<T>::S<T>() { }        // error
    template <class T> S<T>::~S<T>() { }       // okay

The reason for this is that 6.5.5.2 [class.qual] paragraph 2 says that S::S is “considered to name the constructor,” which is not a template and thus cannot accept a template argument list. On the other hand, the second S in S::~S finds the injected-class-name, which “can be used with or without a template-argument-list” (13.8.2 [temp.local] paragraph 1) and thus satisfies the requirement to name the destructor's class (11.4.7 [class.dtor] paragraph 1).

Would it make sense to allow the template-argument-list in the constructor declaration and thus make the language just a little easier to use?

Rationale (July, 2007):

The CWG noted that the suggested change would be confusing in the case where the class template had both template and non-template constructors.