[libcxx-commits] [libcxx] [libc++] Implement Resolution of LWG 3886 (PR #155356)

[A. Jiang via libcxx-commits]

================
@@ -325,6 +325,41 @@ constexpr bool test() {
     }
   }
 
+  // Check move constructor selection
+  {
+    struct MoveOnlyMulti {
+      bool used_move1 = false;
+      bool used_move2 = false;
+
+      constexpr MoveOnlyMulti()                                = default;
+      constexpr MoveOnlyMulti(const MoveOnlyMulti&)            = delete;
+      constexpr MoveOnlyMulti& operator=(const MoveOnlyMulti&) = delete;
+      constexpr MoveOnlyMulti& operator=(MoveOnlyMulti&&) {
+        used_move1 = true;
+        return *this;
+      }
+      constexpr MoveOnlyMulti& operator=(const MoveOnlyMulti&&) {
+        used_move2 = true;
+        return *this;
+      };
+      constexpr MoveOnlyMulti(MoveOnlyMulti&&) : used_move1(true) {}
+      constexpr MoveOnlyMulti(const MoveOnlyMulti&&) : used_move2(true) {}
+    };
+
+    {
+      MoveOnlyMulti t{};
+      std::expected<MoveOnlyMulti, int> e1(std::unexpect);
+      e1 = std::move(t);
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frederick-vs-ja wrote:

Looks like that we should test with `{}`, ditto below. 
```suggestion
      e1 = {std::move(t)};
```

https://github.com/llvm/llvm-project/pull/155356