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* [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression
@ 2020-10-13 12:18 ed at catmur dot uk
2020-10-15 19:02 ` [Bug c++/97402] " ppalka at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: ed at catmur dot uk @ 2020-10-13 12:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97402
Bug ID: 97402
Summary: Value of dependent partial-concept-id is not usable in
a constant expression
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ed at catmur dot uk
Target Milestone: ---
#include <concepts>
template<class T> void f(T x) {
std::same_as<T> auto y = x;
}
int main() { f(1); }
In file included from <source>:1:
<source>: In instantiation of 'void f(T) [with T = int]':
<source>:5:17: required from here
.../gcc-trunk-20201013/include/c++/11.0.0/concepts:57:15: required for the
satisfaction of '__same_as<_Tp, _Up>' [with _Tp = int; _Up = T]
.../gcc-trunk-20201013/include/c++/11.0.0/concepts:57:32: error: the value of
'std::is_same_v<int, T>' is not usable in a constant expression
57 | concept __same_as = std::is_same_v<_Tp, _Up>;
| ~~~~~^~~~~~~~~~~~~~~~~~~
In file included from .../gcc-trunk-20201013/include/c++/11.0.0/concepts:44,
from <source>:1:
.../gcc-trunk-20201013/include/c++/11.0.0/type_traits:3220:25: note:
'std::is_same_v<int, T>' used in its own initializer
3220 | inline constexpr bool is_same_v = __is_same(_Tp, _Up);
| ^~~~~~~~~
<source>:3:26: error: deduced initializer does not satisfy placeholder
constraints
3 | std::same_as<T> auto y = x;
| ^
<source>:3:26: note: constraints not satisfied
https://godbolt.org/z/qGT5xe
Changing std::same_as<T> to std::same_as<int> makes it compile OK.
Feels a little like 96410.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/97402] Value of dependent partial-concept-id is not usable in a constant expression
2020-10-13 12:18 [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression ed at catmur dot uk
@ 2020-10-15 19:02 ` ppalka at gcc dot gnu.org
2021-01-10 13:58 ` kirshamir at gmail dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: ppalka at gcc dot gnu.org @ 2020-10-15 19:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97402
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=96443,
| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=96444
Ever confirmed|0 |1
CC| |ppalka at gcc dot gnu.org
Last reconfirmed| |2020-10-15
Status|UNCONFIRMED |ASSIGNED
--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed. See also PR96443 and PR96444.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/97402] Value of dependent partial-concept-id is not usable in a constant expression
2020-10-13 12:18 [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression ed at catmur dot uk
2020-10-15 19:02 ` [Bug c++/97402] " ppalka at gcc dot gnu.org
@ 2021-01-10 13:58 ` kirshamir at gmail dot com
2021-01-10 14:25 ` kirshamir at gmail dot com
2021-01-18 16:46 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: kirshamir at gmail dot com @ 2021-01-10 13:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97402
Amir Kirsh <kirshamir at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |kirshamir at gmail dot com
--- Comment #2 from Amir Kirsh <kirshamir at gmail dot com> ---
See also:
https://stackoverflow.com/questions/65653983/gcc-stdis-same-vint-t-is-not-usable-in-a-constant-expression
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/97402] Value of dependent partial-concept-id is not usable in a constant expression
2020-10-13 12:18 [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression ed at catmur dot uk
2020-10-15 19:02 ` [Bug c++/97402] " ppalka at gcc dot gnu.org
2021-01-10 13:58 ` kirshamir at gmail dot com
@ 2021-01-10 14:25 ` kirshamir at gmail dot com
2021-01-18 16:46 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: kirshamir at gmail dot com @ 2021-01-10 14:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97402
--- Comment #3 from Amir Kirsh <kirshamir at gmail dot com> ---
Playing with the code even leads to compiler seg-fault, see:
https://stackoverflow.com/a/65654043/2085626
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/97402] Value of dependent partial-concept-id is not usable in a constant expression
2020-10-13 12:18 [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression ed at catmur dot uk
` (2 preceding siblings ...)
2021-01-10 14:25 ` kirshamir at gmail dot com
@ 2021-01-18 16:46 ` ppalka at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-01-18 16:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97402
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |DUPLICATE
Status|ASSIGNED |RESOLVED
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
This is essentially a dup of PR96444, I think.
*** This bug has been marked as a duplicate of bug 96444 ***
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-10-13 12:18 [Bug c++/97402] New: Value of dependent partial-concept-id is not usable in a constant expression ed at catmur dot uk
2020-10-15 19:02 ` [Bug c++/97402] " ppalka at gcc dot gnu.org
2021-01-10 13:58 ` kirshamir at gmail dot com
2021-01-10 14:25 ` kirshamir at gmail dot com
2021-01-18 16:46 ` ppalka at gcc dot gnu.org
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