add move assignment operator for CZString and change copy assignment to const reference.

Author: dhruvCW

include/json/value.h

@@ -233,7 +233,12 @@ class JSON_API Value {
     CZString(CZString&& other);
 #endif
     ~CZString();
-    CZString& operator=(CZString other);
+    CZString& operator=(const CZString& other);
+
+#if JSON_HAS_RVALUE_REFERENCES
+    CZString& operator=(CZString&& other);
+#endif
+
     bool operator<(CZString const& other) const;
     bool operator==(CZString const& other) const;
     ArrayIndex index() const;
@@ -447,7 +452,7 @@ Json::Value obj_value(Json::objectValue); // {}
   /// Equivalent to jsonvalue[jsonvalue.size()] = value;
   Value& append(const Value& value);
 
-#ifdef JSON_HAS_RVALUE_REFERENCES
+#if JSON_HAS_RVALUE_REFERENCES
   Value& append(Value&& value);
 #endif
 

src/lib_json/json_value.cpp

@@ -292,10 +292,20 @@ void Value::CZString::swap(CZString& other) {
   std::swap(index_, other.index_);
 }
 
-Value::CZString& Value::CZString::operator=(CZString other) {
-  swap(other);
+Value::CZString& Value::CZString::operator=(const CZString& other) {
+  cstr_ = other.cstr_;
+  index_ = other.index_;
+  return *this;
+}
+
+#if JSON_HAS_RVALUE_REFERENCES
+Value::CZString& Value::CZString::operator=(CZString&& other) {
+  cstr_ = other.cstr_;
+  index_ = other.index_;
+  other.cstr_ = nullptr;
   return *this;
 }
+#endif
 
 bool Value::CZString::operator<(const CZString& other) const {
   if (!cstr_) return index_ < other.index_;
@@ -1145,7 +1155,7 @@ Value const& Value::operator[](CppTL::ConstString const& key) const
 
 Value& Value::append(const Value& value) { return (*this)[size()] = value; }
 
-#ifdef JSON_HAS_RVALUE_REFERENCES
+#if JSON_HAS_RVALUE_REFERENCES
   Value& Value::append(Value&& value) { return (*this)[size()] = value; }
 #endif