Troubleshoot "dangling pointer" warning in `iterator_interface.t.cpp`

まず src/beman/iterator_interface26/iterator_interface.t.cpp の CI 警告を再現します。特に OperatorArrow の 117 行目を確認し、include/beman/iterator_interface26/detail/stl_interfaces/iterator_interface.hpp の 559 行目にある参照先の実装を調査してください。dangling pointer 診断の原因を特定し、その後、警告がなくなり、関連するテストが引き続き成功することを確認してください。

This warning shows up in the CI job. It was originally pointed out by https://github.com/beman-project/iterator_interface/pull/13#pullrequestreview-2421895988

/home/runner/work/iterator_interface/iterator_interface/src/beman/iterator_interface26/iterator_interface.t.cpp:5:
/home/runner/work/iterator_interface/iterator_interface/src/beman/iterator_interface26/iterator_interface.t.cpp: In member function ‘virtual void beman::iterator_interface26::IteratorTest_OperatorArrow_Test::TestBody()’:
/home/runner/work/iterator_interface/iterator_interface/src/beman/iterator_interface26/iterator_interface.t.cpp:117:20: warning: using a dangling pointer to an unnamed temporary [-Wdangling-pointer=]
  117 |     ASSERT_EQ(ai->f(), 3);
      |               ~~~~~^~
In file included from /home/runner/work/iterator_interface/iterator_interface/include/beman/iterator_interface26/iterator_interface.hpp:8,
                 from /home/runner/work/iterator_interface/iterator_interface/src/beman/iterator_interface26/iterator_interface.t.cpp:2:
/home/runner/work/iterator_interface/iterator_interface/include/beman/iterator_interface26/detail/stl_interfaces/iterator_interface.hpp:559:59: note: unnamed temporary defined here
  559 |           return detail::make_pointer<pointer, reference>(*derived());
      |                                                           ^~~~~~~~~~