https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108579
Bug ID: 108579
Summary: Requires-expression that checks constructor on
non-template constructor of template class got
rejected
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gnaggnoyil at gmail dot com
Target Milestone: ---
template <typename T>
class foo{
public:
foo(double, char){}
foo(int) requires requires { foo(0.0, 'c'); }{}
};
int main(){
foo<int> x(3);
(void)x;
return 0;
}
The above code fails to compile on latest GCC trunk with `-std=c++20` as of the
day of report:
test8.cpp: In instantiation of ‘foo<T>::foo(int) requires requires{foo(0.0,
'c');} [with T = int]’:
test8.cpp:9:17: required from here
test8.cpp:5:5: required by the constraints of ‘template<class T>
foo<T>::foo(int) requires requires{foo(0.0, 'c');}’
test8.cpp:5:23: in requirements [with T = int]
test8.cpp:5:23: error: satisfaction value of atomic constraint
‘requires{foo(0.0, 'c');} [with T = int]’ changed from ‘false’ to ‘true’
5 | foo(int) requires requires { foo(0.0, 'c'); }{}
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
test8.cpp:2:7: note: satisfaction value first evaluated to ‘false’ from here
2 | class foo{
| ^~~
test8.cpp: In function ‘int main()’:
test8.cpp:9:17: error: no matching function for call to ‘foo<int>::foo(int)’
9 | foo<int> x(3);
| ^
test8.cpp:5:5: note: candidate: ‘foo<T>::foo(int) requires requires{foo(0.0,
'c');} [with T = int]’
5 | foo(int) requires requires { foo(0.0, 'c'); }{}
| ^~~
test8.cpp:5:5: note: constraints not satisfied
test8.cpp:4:5: note: candidate: ‘foo<T>::foo(double, char) [with T = int]’
4 | foo(double, char){}
| ^~~
test8.cpp:4:5: note: candidate expects 2 arguments, 1 provided
test8.cpp:2:7: note: candidate: ‘constexpr foo<int>::foo(const foo<int>&)’
2 | class foo{
| ^~~
test8.cpp:2:7: note: no known conversion for argument 1 from ‘int’ to ‘const
foo<int>&’
test8.cpp:2:7: note: candidate: ‘constexpr foo<int>::foo(foo<int>&&)’
test8.cpp:2:7: note: no known conversion for argument 1 from ‘int’ to
‘foo<int>&&’
Replacing the "requires {}" part with "is_constructible<foo, double, char>"
will get rejected too, but with different error messages.
Prior releases of GCC like 12.1 or 12.2 can accept both programs without any
problem.
