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From: "steve+gcc at tecwec dot eu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/104111] [DR2589] Concept evaluation depends on context
 where it was first checked
Date: Thu, 22 Feb 2024 17:11:51 +0000
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X-Bugzilla-Keywords: accepts-invalid, rejects-valid, wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104111

Eric Estievenart <steve+gcc at tecwec dot eu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |steve+gcc at tecwec dot eu

--- Comment #9 from Eric Estievenart <steve+gcc at tecwec dot eu> ---
By the way, the following code exhibits another related weirdness, without
access control being involved:
```
#include <concepts>
struct Op
{
        void operator()( auto x ) const =3D delete; // want only explicit
customization in scope
};

struct S {};
static_assert( !std::invocable<Op, S> );
template<> void Op::operator()( S ) const {}  // now Op is invocable on S
static_assert( std::invocable<Op, S> );       // so should not fail ! but...
```
(https://godbolt.org/z/Wa6rxeMvP)

Commenting the first assert makes the second suddenly pass...

Quantum physicist would say "spooky action at a distance" ;-)
Hope this helps,
Best.=