implement LWG-3527 (#2194)

Co-authored-by: Adam Bucior <35536269+AdamBucior@users.noreply.github.com> Co-authored-by: Alex Guteniev <gutenev@gmail.com> Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
microsoft · Sep 11, 2021 · 1a985bc · 1a985bc
1 parent 75e7d21
commit 1a985bc
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Showing 2 changed files with 15 additions and 3 deletions.
diff --git a/stl/inc/xmemory b/stl/inc/xmemory
@@ -2140,10 +2140,10 @@ template <class _Ty, class _Alloc, class _Uty1, class _Uty2, enable_if_t<_Is_spe
 _NODISCARD constexpr auto uses_allocator_construction_args(const _Alloc& _Al, pair<_Uty1, _Uty2>&& _Pair) noexcept {
     // equivalent to
     // return _STD uses_allocator_construction_args<_Ty>(_Al, piecewise_construct,
-    //     _STD forward_as_tuple(_STD move(_Pair).first), _STD forward_as_tuple(_STD move(_Pair).second));
+    //     _STD forward_as_tuple(_STD get<0>(_STD move(_Pair)), _STD forward_as_tuple(_STD get<1>(_STD move(_Pair)));
     return _STD make_tuple(piecewise_construct,
-        _STD uses_allocator_construction_args<typename _Ty::first_type>(_Al, _STD move(_Pair).first),
-        _STD uses_allocator_construction_args<typename _Ty::second_type>(_Al, _STD move(_Pair).second));
+        _STD uses_allocator_construction_args<typename _Ty::first_type>(_Al, _STD get<0>(_STD move(_Pair))),
+        _STD uses_allocator_construction_args<typename _Ty::second_type>(_Al, _STD get<1>(_STD move(_Pair))));
 }
 
 template <class _Ty, class _Alloc, class... _Types>

diff --git a/tests/std/tests/P0475R1_P0591R4_uses_allocator_construction/test.cpp b/tests/std/tests/P0475R1_P0591R4_uses_allocator_construction/test.cpp
@@ -179,6 +179,18 @@ void test_GH_2021() { // COMPILE-ONLY
     tags[0];
 }
 
+struct MoveOnlyType {
+    MoveOnlyType()               = default;
+    MoveOnlyType(MoveOnlyType&&) = default;
+};
+
+void test_LWG3527() { // COMPILE-ONLY
+    allocator<MoveOnlyType> alloc;
+    MoveOnlyType obj;
+    pair<MoveOnlyType&&, MoveOnlyType&&> p{move(obj), move(obj)};
+    [[maybe_unused]] auto t = uses_allocator_construction_args<pair<MoveOnlyType&&, MoveOnlyType&&>>(alloc, move(p));
+}
+
 int main() {
     test_P0475R1();