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From: "fchelnokov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107168] New: Wrong errors for concepts with default lambda
 not-type argument
Date: Thu, 06 Oct 2022 07:08:01 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 12.2.0
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X-Bugzilla-Who: fchelnokov at gmail dot com
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107168

            Bug ID: 107168
           Summary: Wrong errors for concepts with default lambda not-type
                    argument
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

The following code in accepted in Clang and MSVC, but GCC emits seemingly w=
rong
errors:

template <typename, auto =3D []{}> concept x =3D true;
struct S {
    // GCC error: template argument 2 is invalid
    operator x auto() { return 42; }
    // GCC error: wrong number of template arguments (0, should be at least=
 1)
    operator x<> auto() const { return 43; }
};

Online demo: https://godbolt.org/z/a3494qrG3=