[gcc r15-11259] libstdc++: Use ranges::iter_move in ranges::unique [PR120789]

[Patrick Palka]

https://gcc.gnu.org/g:dca6d147d8b1ce3860635375b492bb80a511deaa

commit r15-11259-gdca6d147d8b1ce3860635375b492bb80a511deaa
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Jul 1 13:43:09 2025 -0400

    libstdc++: Use ranges::iter_move in ranges::unique [PR120789]
    
            PR libstdc++/120789
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/ranges_algo.h (__unique_fn::operator()): Use
            ranges::iter_move(iter) instead of std::move(*iter).
            * testsuite/25_algorithms/unique/120789.cc: New test.
    
    Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    (cherry picked from commit 6f69a68998f601cdb86c65113eb1feddfa9da31a)

Diff:
---
 libstdc++-v3/include/bits/ranges_algo.h            |  2 +-
 .../testsuite/25_algorithms/unique/120789.cc       | 36 ++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 7b1408452128..3bf3cf2f102b 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -1173,7 +1173,7 @@ namespace ranges
 	  if (!std::__invoke(__comp,
 			     std::__invoke(__proj, *__dest),
 			     std::__invoke(__proj, *__first)))
-	    *++__dest = std::move(*__first);
+	    *++__dest = ranges::iter_move(__first);
 	return {++__dest, __first};
       }
 
diff --git a/libstdc++-v3/testsuite/25_algorithms/unique/120789.cc b/libstdc++-v3/testsuite/25_algorithms/unique/120789.cc
new file mode 100644
index 000000000000..24b107132473
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/unique/120789.cc
@@ -0,0 +1,36 @@
+// PR libstdc++/120789 - ranges::unique should use ranges::iter_move
+// { dg-do compile { target c++20 } }
+
+#include <algorithm>
+
+struct A
+{
+  bool operator==(const A&) const;
+};
+
+struct B
+{
+  B(B&&) = delete;
+  B& operator=(const A&) const;
+
+  operator A() const;
+  bool operator==(const B&) const;
+};
+
+struct I
+{
+  using value_type = A;
+  using difference_type = int;
+  B operator*() const;
+  I& operator++();
+  I operator++(int);
+  bool operator==(const I&) const;
+  friend A iter_move(const I&);
+};
+
+void
+test01()
+{
+  std::ranges::subrange<I, I> r;
+  auto [begin, end] = std::ranges::unique(r);
+}