https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99909
Bug ID: 99909
Summary: The value of 'std::is_integral_v<auto>' 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: hewillk at gmail dot com
Target Milestone: ---
https://godbolt.org/z/jWr39rrsT
#include <concepts>
template <std::integral auto>
struct S {};
template <template <std::integral auto> class>
constexpr auto f() {}
int main() {
f<S>();
}
gcc rejects this code with:
In file included from <source>:1:
/opt/compiler-explorer/gcc-trunk-20210404/include/c++/11.0.1/concepts:102:13:
required for the satisfaction of 'integral<auto [requires
std::integral<<placeholder>, >]>' [with auto [requires
std::integral<<placeholder>, >] = auto [requires std::integral<<placeholder>,
>]]
/opt/compiler-explorer/gcc-trunk-20210404/include/c++/11.0.1/concepts:102:24:
error: the value of 'std::is_integral_v<auto [requires
std::integral<<placeholder>, >]>' is not usable in a constant expression
102 | concept integral = is_integral_v<_Tp>;
| ^~~~~~~~~~~~~~~~~~
In file included from
/opt/compiler-explorer/gcc-trunk-20210404/include/c++/11.0.1/concepts:44,
from <source>:1:
/opt/compiler-explorer/gcc-trunk-20210404/include/c++/11.0.1/type_traits: In
function 'int main()':
/opt/compiler-explorer/gcc-trunk-20210404/include/c++/11.0.1/type_traits:3026:25:
note: 'std::is_integral_v<auto [requires std::integral<<placeholder>, >]>' used
in its own initializer
3026 | inline constexpr bool is_integral_v = is_integral<_Tp>::value;
| ^~~~~~~~~~~~~
