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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106644] [C++23] P2468R2 - The Equality Operator You Are
 Looking For
Date: Sat, 22 Oct 2022 13:11:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106644

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
As for implementation, I'd say in call.cc (add_candidates) we could do
something like:
  if ((flags & (LOOKUP_REWRITTEN | LOOKUP_REVERSE))
      && DECL_OVERLOADED_OPERATOR_IS (fn, EQ_EXPR))
    {
    }

before the loop on the overloads and depending on whether fn is in class sc=
ope
or namespace scope perform lookup (again argument dependent or not?) for
ovl_op_identifier (false, NE_EXPR) in the same scope.
But am not really sure what to do next if this finds something (supposedly =
in
the loop over the overloads?); I suppose if no template is involved, compare
the argument types (what else?), but for templates it is unclear (to me) if=
 it
should try to instantiate them and compare types only afterwards, or what
exactly should be checked whether they correspond ([basic.scope.scope]).
Because e.g. http://eel.is/c++draft/basic.scope.scope#4.3.1 talks about
equivalent trailing requires clauses etc.=