https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112749
Bug ID: 112749
Summary: GCC accepts invalid code in concepts (requires clause
incorrectly satisfied)
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: novulae at hotmail dot com
Target Milestone: ---
The below example is ill-formed - the requires clause should not be satisfied
due to the failure to instantiate W1<int>, but GCC accepts the code
nonetheless.
Clang rejects the code.
$ cat gcc-bug.cpp
template<class> concept C1 = true;
template<class T> using W1 = decltype(nonexistent<T>(0));
template<class T>
requires C1<W1<T>>
void func(T);
void test() {
func(0);
}
$ g++ -c -std=c++20 gcc-bug.cpp
$ clang++ -c -std=c++20 gcc-bug.cpp
gcc-bug.cpp:10:3: error: no matching function for call to 'func'
10 | func(0);
| ^~~~
gcc-bug.cpp:7:6: note: candidate template ignored: constraints not satisfied
[with T = int]
7 | void func(T);
| ^
gcc-bug.cpp:3:39: note: because substituted constraint expression is
ill-formed: use of undeclared identifier 'nonexistent'
3 | template<class T> using W1 = decltype(nonexistent<T>(0));
| ^
1 error generated.
