[libc++] Make the constraints as intended.

[philnik]

Please add tests for this under libcxx/test/std/iterators/iterator.requirements/iterator.cust/iterator.cust.move/.

[cjdb]

Can you please provide a descriptive subject line about what has changed for the commit? It should also be prefixed with [libcxx] or [libc++].

[K1ZeKaTo]

The constraints do not work while rvalue.

[K1ZeKaTo]

Modify to pass tests.

[K1ZeKaTo]

Try to fix CI.

[K1ZeKaTo]

Try to fix CI.

[cjdb]

I'm still not quite sure what problem this patch aims to solve. Would you please be able to provide a commit description that describes the problem that's being solved in some detail?

[cjdb]

The changes in the header seem correct to me, but we can't move forward till the commit message has been fixed.

libcxx/test/std/iterators/iterator.requirements/iterator.cust/iterator.cust.move/iter_move_rvalue.compile.pass.cpp

1 ↗

(On Diff #547466)

I'd prefer that this be a runtime test, since it's something that needs to work in both cases. As such, we'll need to rework this test so it handles runtime too.

libcxx/include/__iterator/iter_move.h

requires (_Tp&& __t) {
     // NOLINTNEXTLINE(libcpp-robust-against-adl) iter_swap ADL calls should only be made through ranges::iter_swap
     iter_move(std::forward<_Tp>(__t));
   };
 
 template<class _Tp>
 concept __move_deref =
   !__unqualified_iter_move<_Tp> &&
   requires (_Tp&& __t) {
-    *__t;
-    requires is_lvalue_reference_v<decltype(*__t)>;
+    *std::forward<_Tp>(__t);
+    requires is_lvalue_reference_v<decltype(*std::forward<_Tp>(__t))>;
   };
 
 template<class _Tp>
 concept __just_deref =
   !__unqualified_iter_move<_Tp> &&
   !__move_deref<_Tp> &&
   requires (_Tp&& __t) {
-    *__t;
-    requires (!is_lvalue_reference_v<decltype(*__t)>);
+    *std::forward<_Tp>(__t);
+    requires (!is_lvalue_reference_v<decltype(*std::forward<_Tp>(__t))>);
   };
 
 // [iterator.cust.move]
 
 struct __fn {
   // NOLINTBEGIN(libcpp-robust-against-adl) iter_move ADL calls should only be made through ranges::iter_move
   template<class _Ip>
     requires __unqualified_iter_move<_Ip>

libcxx/test/std/iterators/iterator.requirements/iterator.cust/iterator.cust.move/iter_move.rvalue.verify.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// Test the constraints in libc++.
+
+// template<class I>
+// unspecified iter_move;
+
+#include <array>
+#include <utility>
+#include <iterator>
+
+template <typename I>
+class wrapper {
+public:
+  wrapper() = default;
+
+  constexpr explicit wrapper(I i) noexcept : base_(std::move(i)) {}
+
+  // This operator is used to check the constraints work.
+  constexpr decltype(auto) operator*() & noexcept { return base_; }
+
+  // This operator is used to check the constraints work.
+  constexpr auto&& operator*() && noexcept = delete;
+
+private:
+  I base_ = I{};
+};
+
+void test_iter_move_rvalue_verify() {
+  std::array<int, 1> t1;
+  auto first = wrapper{std::move(t1)};
+
+  auto helper = [](auto&& first) requires (!requires{std::ranges::iter_move(std::move(first));}) {};
+  auto _ = std::ranges::iter_move(first);
+  helper(first);
+}