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From: "fchelnokov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/115280] New: Concept can access private alias in a classs
Date: Wed, 29 May 2024 16:31:05 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 14.1.1
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115280

            Bug ID: 115280
           Summary: Concept can access private alias in a classs
           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
```
#include <concepts>

class A {
    using X =3D int;
};

template<typename T>
concept C =3D requires(T t) {
    { t } -> std::convertible_to<A::X>;
};

static_assert(C<int>);
```
is invalid and rejected by Clang with the error:
> error: 'X' is a private member of 'A'

But GCC accepts the program just fine, which looks wrong, online demo:
https://gcc.godbolt.org/z/nra6fExxG=