Give WalletModel::UnlockContext move semantics

Author: sipa

src/qt/walletmodel.cpp

@@ -482,7 +482,7 @@ WalletModel::UnlockContext::~UnlockContext()
     }
 }
 
-void WalletModel::UnlockContext::CopyFrom(const UnlockContext& rhs)
+void WalletModel::UnlockContext::CopyFrom(UnlockContext&& rhs)
 {
     // Transfer context; old object no longer relocks wallet
     *this = rhs;

src/qt/walletmodel.h

@@ -194,15 +194,18 @@ class WalletModel : public QObject
 
         bool isValid() const { return valid; }
 
-        // Copy operator and constructor transfer the context
-        UnlockContext(const UnlockContext& obj) { CopyFrom(obj); }
-        UnlockContext& operator=(const UnlockContext& rhs) { CopyFrom(rhs); return *this; }
+        // Copy constructor is disabled.
+        UnlockContext(const UnlockContext&) = delete;
+        // Move operator and constructor transfer the context
+        UnlockContext(UnlockContext&& obj) { CopyFrom(std::move(obj)); }
+        UnlockContext& operator=(UnlockContext&& rhs) { CopyFrom(std::move(rhs)); return *this; }
     private:
         WalletModel *wallet;
         bool valid;
         mutable bool relock; // mutable, as it can be set to false by copying
 
-        void CopyFrom(const UnlockContext& rhs);
+        UnlockContext& operator=(const UnlockContext&) = default;
+        void CopyFrom(UnlockContext&& rhs);
     };
 
     UnlockContext requestUnlock();