[class.mem] Deduction guides do not declare new members #3932
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| @@ -513,6 +513,8 @@ | |||
| if it is | |||
| \begin{itemize} | |||
| \item a friend declaration\iref{class.friend}, | |||
| \item a \grammarterm{deduction-guide}\iref{temp.deduct.guide}, | |||
| \item a \grammarterm{template-declaration} whose \grammarterm{declaration} is one of the above, | |||
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I agree that a deduction-guide does not declare a new member (as explained in the commit comment), but here materializes another rule that isn't mentioned. (Plus, it seems to me a template friend is still a friend declaration of sorts.)
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Please don't mix unrelated changes in the same commit.
I wouldn't say that it's entirely unrelated, so should I just change the commit message & PR name?
It seems to me a template friend is still a friend declaration of sorts.
I consider a friend template to be a friend declaration as much as I consider a class template to be a class declaration.
here materializes another rule that isn't mentioned
I'm assuming that you're referring to deduction-guides declared outside of a template-declaration. With respect to such declarations, I don't see any wording (normative or informative) that explicitly states such deduction-guides can be declared, however we can deduce that it's allowed from:
- grammar (a deduction-guide (without a template-head) is a declaration as well as a member-declaration) and,
- normative wording ([over.match.class.deduct] p1.4 says "if any" when referring to the template parameters; you can't explicitly specialize a deduction guide so the only context where this would occur is when there is no template-head)
The intent in P0091R3 is pretty clear (emphasis mine):