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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110580] [14 Regression] gcc fails to typecheck nix-2.16.1
 source: error: invalid initialization of reference of type
Date: Sun, 09 Jul 2023 18:37:05 +0000
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X-Bugzilla-Keywords: needs-bisection, rejects-valid
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110580

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Slightly more reduced:
```
#include <type_traits>

using std::is_same_v;

struct s0 {};
struct s1 {};
template <typename _Key>=20
struct s3 {
  template <typename _Up, typename _Vp =3D _Up>
  static constexpr bool __usable_key =3D is_same_v<_Vp, _Key>;
  static_assert(!__usable_key<s1>);
};
s3<s0> t;

```
If I remove _Vp or remove it from being type dependent, it works.=