[gcc/devel/ranger] libstdc++: Improve comment about testsuite utilities

[gcc/devel/ranger] libstdc++: Improve comment about testsuite utilities

[Aldy Hernandez]

https://gcc.gnu.org/g:68be73fc42b969d8d595aeda98e3ea962a7a9ed5

commit 68be73fc42b969d8d595aeda98e3ea962a7a9ed5
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Jan 10 22:10:48 2020 +0000

    libstdc++: Improve comment about testsuite utilities
    
    This fixes a typo and also explains why test_container is not a range
    when used with output_iterator_wrapper or input_iterator_wrapper.
    
            * testsuite/util/testsuite_iterators.h: Improve comment.
    
    From-SVN: r280146

Diff:
---
 libstdc++-v3/ChangeLog                            |  2 ++
 libstdc++-v3/testsuite/util/testsuite_iterators.h | 11 +++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 3d25ecc3da1..79a5887f7d0 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,7 @@
 2020-01-10  Jonathan Wakely  <jwakely@redhat.com>
 
+	* testsuite/util/testsuite_iterators.h: Improve comment.
+
 	* testsuite/25_algorithms/equal/deque_iterators/1.cc: Don't use C++11
 	initialization syntax.
 
diff --git a/libstdc++-v3/testsuite/util/testsuite_iterators.h b/libstdc++-v3/testsuite/util/testsuite_iterators.h
index e01d7daea5d..eb15257bf6a 100644
--- a/libstdc++-v3/testsuite/util/testsuite_iterators.h
+++ b/libstdc++-v3/testsuite/util/testsuite_iterators.h
@@ -759,10 +759,13 @@ namespace __gnu_test
     using test_output_sized_range
       = test_sized_range<T, output_iterator_wrapper>;
 
-// test_container, test_range and test_sized_range do not own their elements,
-// so they all model std::ranges::safe_range. This file does not define
-// specializations of std::ranges::enable_safe_range, so that individual
-// test can decide whether or not to do so.
+// test_range and test_sized_range do not own their elements, so they model
+// std::ranges::safe_range.  This file does not define specializations of
+// std::ranges::enable_safe_range, so that individual tests can decide
+// whether or not to do so.
+// This is also true for test_container, although only when it has forward
+// iterators (because output_iterator_wrapper and input_iterator_wrapper are
+// not default constructible so do not model std::input_or_output_iterator).
 #endif // C++20
 } // namespace __gnu_test
 #endif // _TESTSUITE_ITERATORS