[PATCH] Add safe iterator iterator_concept

[François Dumont]

I plan to commit this patch tomorrow.

    * include/debug/safe_iterator.h
[__cpp_lib_concepts](_Safe_iterator<>::iterator_concept): Define for
    C++20.

François


diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index 685256551d9..abf575186c7 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -141,6 +141,10 @@ namespace __gnu_debug
       typedef typename _Traits::reference		reference;
       typedef typename _Traits::pointer			pointer;
 
+#if __cplusplus > 201703L && __cpp_lib_concepts
+      using iterator_concept = std::__detail::__iter_concept<_Iterator>;
+#endif
+
       /// @post the iterator is singular and unattached
       _Safe_iterator() _GLIBCXX_NOEXCEPT : _Iter_base() { }