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4443. Clean up identifier comparisons in meta::define_aggregate

Section: 21.4.16 [meta.reflection.define.aggregate] Status: Immediate Submitter: Tomasz Kamiński Opened: 2025-11-04 Last modified: 2025-11-04

Priority: Not Prioritized

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Discussion:

N_K is defined as an identifier (see 11.4.1) and should not be compared with code or with string literals in bullet 8.4. Similarly, 9.5.1 should not talk about “character sequence encoded by N_K”

[Kona 2025-11-04; approved by LWG. Status changed: New → Immediate.]

Proposed resolution:

This wording is relative to N5014.

1. Modify 21.4.16 [meta.reflection.define.aggregate] as indicated:

   template<reflection_range R = initializer_list<info>>
     consteval info define_aggregate(info class_type, R&& mdescrs);
   

   -7- […]

   -8- Constant When:

   • -8.1- […]
   • -8.2- […]
   • -8.3- […]
   • -8.4- for every pair (r_K, r_L) where K<L, if N_K is not ⊥ and N_L is not ⊥, then either:
     • -8.4.1- N_K != N_L is true N_K is not the same identifier as N_L or
     • -8.4.2- N_K == u8"_" is true N_K is the identifier _ (u+005f low line).

   -9- Effects: Produces an injected declaration D (7.7 [expr.const]) that defines C and has properties as follows:

   • -9.1- […]
   • -9.2- […]
   • -9.3- […]
   • -9.4- […]
   • -9.5- for every r_K, there is corresponding entity M_K belonging to the class scope of D with the following properties: K<L, if N_K is not ⊥ and N_L is not ⊥, then either:
     • -9.5.1- if N_K is ⊥, M_K is an unnamed bit-field. Otherwise, M_K is a non-static data member whose name is the identifier determined by the character sequence encoded by N_K in UTF-8.
     • -9.5.2- […]
     • -9.5.3- […]
     • -9.5.4- […]
     • -9.5.5- […]
   • -9.6- […]