Created on 2025-04-14.00:00:00 last changed 3 weeks ago
Proposed resolution (approved by CWG 2026-05-19):
Change and merge in 13.6 [temp.type] paragraph 5 and paragraph 6 as follows:
For a type template parameter pack T, T...[constant-expression] denotes a unique dependent type.If the constant-expression of a pack-index-specifier is value-dependent, twoTwo such pack-index-specifiers (9.2.9.4 [dcl.type.pack.index]) refer to the same type only if
- their typedef-names refer to the same template parameter pack and
- if neither of their constant-expressions is value-dependent, then they have the same value, otherwise their constant-expressions are equivalent (13.7.7.2 [temp.over.link]).
Otherwise, two such pack-index-specifier s refer to the same type only if their indexes have the same value.
(From submission #700.)
Subclause 13.6 [temp.type] paragraph 5 and paragraph 6 specify:
For a type template parameter pack T, T...[constant-expression] denotes a unique dependent type.
If the constant-expression of a pack-index-specifier is value-dependent, two such pack-index-specifiers refer to the same type only if their constant-expressions are equivalent (13.7.7.2 [temp.over.link]). Otherwise, two such pack-index-specifier s refer to the same type only if their indexes have the same value.
That seems to imply that pack-index-specifiers referring to different template parameter packs could be equivalent.
| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2026-05-19 17:41:16 | admin | set | status: open -> tentatively ready |
| 2025-11-06 23:04:52 | admin | set | messages: + msg8359 |
| 2025-04-14 00:00:00 | admin | create | |