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

2650. Incorrect example for ill-formed non-type template arguments

[Accepted as a DR at the November, 2022 meeting.]

The example intends to illustrate that a class type cannot be the type of a non-type template parameter (although the example is still ill-formed because "T()" is interpreted as a function type).

Proposed resolution (approved by CWG 2022-11-08):

Change in 13.10.3.1 [temp.deduct.general] bullet 11.8 as follows:

• ...
• Attempting to give an invalid type to a non-type template parameter. [Example 13:

    template <class T, T> struct S {};
    template <class T> int f(S<T, T()T{}>*);   // #1
    class X {
      int m;
    };
    int i0 = f<X>(0);   // #1 uses a value of non-structural type X as a non-type template argument
  

  -- end example ]
• ...