https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127799
Bug ID: 127799
Summary: constexpr local used in requires-clause rejected
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mpolacek at gcc dot gnu.org
Target Milestone: ---
```
void g(auto x) {
constexpr int n = sizeof(x);
auto v = [](auto t) requires (n > 0) {};
v(0);
}
int main() { g(0); }
```
is wrongly rejected with
bug1.C: In substitution of ‘template<class auto:2>
g<int>(int)::<lambda(auto:2)> [with auto:2 = int]’:
bug1.C:4:4: required from ‘void g(auto:1) [with auto:1 = int]’
4 | v(0);
| ~^~~
bug1.C:7:15: required from here
7 | int main() { g(0); }
| ~^~~
bug1.C:3:12: required by the constraints of ‘template<class auto:1>
template<class auto:2> g(auto:1)::<lambda(auto:2)>’
3 | auto v = [](auto t) requires (n > 0) {};
| ^
bug1.C:3:33: error: the value of ‘n’ is not usable in a constant expression
3 | auto v = [](auto t) requires (n > 0) {};
| ^
bug1.C:2:17: note: ‘n’ used in its own initializer
2 | constexpr int n = sizeof(x);
| ^
bug1.C: In instantiation of ‘void g(auto:1) [with auto:1 = int]’:
bug1.C:7:15: required from here
7 | int main() { g(0); }
| ~^~~
bug1.C:4:4: error: no match for call to ‘(g<int>(int)::<lambda(auto:2)>) (int)’
4 | v(0);
| ~^~~
• there is 1 candidate
bug1.C:3:13:
3 | auto v = [](auto t) requires (n > 0) {};
| ^
• candidate 1: ‘template<class auto:2> g<int>(int)::<lambda(auto:2)>’
bug1.C:3:12:
3 | auto v = [](auto t) requires (n > 0) {};
| ^
• substitution of deduced template arguments resulted in errors seen
above
Clang/EDG/MSVC accept the code.
