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From: "johelegp at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110211] New: Local lambda treated as non-local
Date: Sun, 11 Jun 2023 16:42:37 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: c++-lambda, rejects-valid
X-Bugzilla-Severity: normal
X-Bugzilla-Who: johelegp 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=3D110211

            Bug ID: 110211
           Summary: Local lambda treated as non-local
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: c++-lambda, rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See <https://compiler-explorer.com/z/W9PzEcc1v>.

```C++
template<class F, class T> concept invocable =3D requires(F f, T x) { f(x);=
 };
static_assert(!invocable<
              decltype([]<class T>(T) -> decltype([&]<class U>(U x)
                                                    requires requires { x.a=
();
}
                                                  {}(T())) {}),
                       int>);
```

```output
<source>:3:52: error: non-local lambda expression cannot have a capture-def=
ault
    3 |               decltype([]<class T>(T) -> decltype([&]<class U>(U x)
      |                                                    ^
Compiler returned: 1
```

According to <https://eel.is/c++draft/expr.prim.lambda#capture-3>, this sho=
uld
work.
If the `static_assert` is in a function, it still fails:
<https://compiler-explorer.com/z/b7rdqfxed>.
It fails on GCC10: <https://compiler-explorer.com/z/znsYvKdz1>.=