https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107471
Bug ID: 107471
Summary: mismatching constraints in common_iterator
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: h2+bugs at fsfe dot org
Target Milestone: ---
In bits/stl_iterator.h:
```cpp
/// An iterator/sentinel adaptor for representing a non-common range.
template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
requires (!same_as<_It, _Sent>) && copyable<_It>
class common_iterator
{
// ...
template<input_or_output_iterator _It2, sentinel_for<_It2> _Sent2>
friend class common_iterator;
```
The constraints are mismatching. GCC (falsely) accepts this, but clang fails,
see also
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107470
