[Bug c++/116310] New: default equality operator== selects not-const conversion operator

[Bug c++/116310] New: default equality operator== selects not-const conversion operator

[fchelnokov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116310

            Bug ID: 116310
           Summary: default equality operator== selects not-const
                    conversion operator
           Product: gcc
           Version: 14.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

This program
```
struct A {
    int i = 0;
    constexpr operator int() const { return i; }
    constexpr operator int&() { return ++i; }
};

struct B {
    A a;
    bool operator==(const B &) const = default;
};

constexpr bool f() {
    B x;
    return x == x;
}

static_assert( f() ); // fails in GCC
```
is accepted by Clang and MSVC, but fails static assertion in GCC. Online demo:
https://gcc.godbolt.org/z/4xjTnM54M

GCC looks wrong here, because not-const `operator int&` should not be called
from within `B::operator==(const B &) const`.

Original discussion: https://stackoverflow.com/q/78850335/7325599

[Bug c++/116310] default equality operator== selects not-const conversion operator

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116310

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jlame646 at gmail dot com

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 116311 has been marked as a duplicate of this bug. ***

[Bug c++/116310] default equality operator== const selects not-const conversion operator

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116310

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|default equality operator== |default equality operator==
                   |selects not-const           |const selects not-const
                   |conversion operator         |conversion operator
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-08-09
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. Looks like the const on the default operator== is being ignored
incorrectly.