https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113470
Bug ID: 113470
Summary: Should std::tuple_size<const int> be a complete type?
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: de34 at live dot cn
Target Milestone: ---
The following code snippet is currently showing implementation divergence
(https://godbolt.org/z/P8oWqf5sT). MSVC STL's std::tuple_size<const int> is a
complete type, while libstdc++'s and libc++'s are not.
```
#include <tuple>
// constexpr auto foo = sizeof(std::tuple_size<int>); // Correctly rejected.
constexpr auto bar = sizeof(std::tuple_size<const int>); // Should be
well-formed?
```
It seems that MSVC STL's behavior is justified by
https://eel.is/c++draft/contents#1 and https://eel.is/c++draft/tuple.syn, given
that only the primary templates of std::tuple_size and std::tuple_element are
marked `// not defined`.
I'm not sure whether this should be considered as a bug. Perhaps an LWG issue
is wanted.
