[Bug c++/106791] New: [12 Regression] Operator Lookup with using namespace

[Bug c++/106791] New: [12 Regression] Operator Lookup with using namespace

[gcc at hazardy dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106791

            Bug ID: 106791
           Summary: [12 Regression] Operator Lookup with using namespace
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at hazardy dot de
  Target Milestone: ---

My Catch Testprojects fail with GCC 12, some in a namespace provided
equality-operators which are brought into the gobal namespace with "using
namespace" are not found anymore.

I have narrowed down to: https://godbolt.org/z/GqnvYMGYq
I was not able to narrow it down without using Catch.
If you define WorkAround it compiles with GCC 11 and 12.

#include <catch.hpp>

struct Type1 {};

struct Type2 {};

namespace Op {
    bool operator==(const Type1&, const Type2&);
}

//#define WorkAround
#ifndef WorkAround
using namespace Op;
#else
bool operator==(const Type1& t1, const Type2& t2) {
    return Op::operator==(t1, t2);
}
#endif

TEST_CASE("") {
    Type1 t1;
    Type2 t2;

    CHECK(t1 == t2);
}

[Bug c++/106791] [12/13 Regression] Operator Lookup with using namespace

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106791

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[12 Regression] Operator    |[12/13 Regression] Operator
                   |Lookup with using namespace |Lookup with using namespace
   Target Milestone|---                         |12.3
           Keywords|                            |rejects-valid

[Bug c++/106791] [12/13 Regression] Operator Lookup with using namespace since r12-702-g6ab1176667734bd6

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106791

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org
            Summary|[12/13 Regression] Operator |[12/13 Regression] Operator
                   |Lookup with using namespace |Lookup with using namespace
                   |                            |since
                   |                            |r12-702-g6ab1176667734bd6
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-08-31

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r12-702-g6ab1176667734bd6.

[Bug c++/106791] [12/13 Regression] Operator Lookup with using namespace since r12-702-g6ab1176667734bd6

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106791

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is not a valid testcase for a GCC bug report. As requested when creating
the bug, please read https://gcc.gnu.org/bugs and provide the missing info next
time.

The example can be reduced to:

namespace test
{
  template<class T, class U>
    bool checkEqual(const T& t, const U& u)
    {
      return t == u;
    }
}

struct Type1 {};

struct Type2 {};

namespace Op {
    bool operator==(const Type1&, const Type2&);
}

//#define WorkAround
#ifndef WorkAround
using namespace Op;
#else
bool operator==(const Type1& t1, const Type2& t2) {
    return Op::operator==(t1, t2);
}
#endif

bool fixture()
{
  Type1 t1;
  Type2 t2;

  return test::checkEqual(t1, t2);
}

GCC is correct to reject this. GCC 11 and older releases had a bug in name
lookup for operators, which has been fixed. See PR51577 for more info.

Clang also rejects your code, with a similar error.

[Bug c++/106791] [12/13 Regression] Operator Lookup with using namespace since r12-702-g6ab1176667734bd6

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106791

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Closing as invalid.