[Bug c++/59256] qualified name in friend function declaration doesn't match previous declaration in inline namespace

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59256

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm going to commit a workaround in <bits/regex.h> so I don't do this again.

--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -62,6 +62,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename, typename, typename, bool>
     class _Executor;

+#ifdef _GLIBCXX_INLINE_VERSION
+#define _GLIBCXX_NAMESPACE_VERSION __7::
+#else
+#define _GLIBCXX_NAMESPACE_VERSION
+#endif
 _GLIBCXX_END_NAMESPACE_VERSION
 }

@@ -770,7 +775,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       template<typename _Bp, typename _Ap, typename _Cp, typename _Rp,
        __detail::_RegexExecutorPolicy, bool>
        friend bool
-       __detail::__regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
+       __detail:: _GLIBCXX_NAMESPACE_VERSION
+        __regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
                                    const basic_regex<_Cp, _Rp>&,
                                    regex_constants::match_flag_type);

@@ -1861,7 +1867,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       template<typename _Bp, typename _Ap, typename _Cp, typename _Rp,
        __detail::_RegexExecutorPolicy, bool>
        friend bool
-       __detail::__regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
+       __detail:: _GLIBCXX_NAMESPACE_VERSION
+        __regex_algo_impl(_Bp, _Bp, match_results<_Bp, _Ap>&,
                                    const basic_regex<_Cp, _Rp>&,
                                    regex_constants::match_flag_type);