https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119075
Bug ID: 119075
Summary: LWG4140 seems incompletely implemented
Product: gcc
Version: 15.0
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: ---
As of LWG4140, the following code snippet should be accepted, but libstdc++ is
still rejecting it because the private default constructor of
std::vector<bool>::reference isn't removed yet.
https://godbolt.org/z/3bnaqrreW
```
#include <bitset>
#include <vector>
#include <type_traits>
int test1(std::bitset<42>::reference);
void test1(std::enable_if<false>);
static_assert(std::is_same<decltype(test1({})), void>::value, "");
int test2(std::vector<bool>::reference);
void test2(std::enable_if<false>);
static_assert(std::is_same<decltype(test2({})), void>::value, "");
```
I think the existence of private or delete default constructor is somehow
observable, see also LWG3160 (https://cplusplus.github.io/LWG/issue3160).
