Add another rvalue constructor to the String class

refs #12555

lib/base/string.cpp

@@ -29,6 +29,23 @@ REGISTER_BUILTIN_TYPE(String, String::GetPrototype());
 
 const String::SizeType String::NPos = std::string::npos;
 
+String::String(Value&& other)
+{
+	*this = std::move(other);
+}
+
+String& String::operator=(Value&& other)
+{
+	const String *p = other.GetPtr<String>();
+
+	if (p)
+		m_Data = std::move(p->m_Data);
+	else
+		m_Data = other;
+
+	return *this;
+}
+
 String& String::operator+=(const Value& rhs)
 {
 	m_Data += static_cast<String>(rhs);

lib/base/string.hpp

@@ -85,6 +85,8 @@ public:
 		: m_Data(std::move(other.m_Data))
 	{ }
 
+	String(Value&& other);
+
 	inline ~String(void)
 	{ }
 
@@ -105,6 +107,8 @@ public:
 		return *this;
 	}
 
+	String& operator=(Value&& rhs);
+
 	inline String& operator=(const std::string& rhs)
 	{
 		m_Data = rhs;

lib/base/value.hpp

@@ -286,6 +286,12 @@ public:
 		return boost::get<T>(m_Value);
 	}
 
+	template<typename T>
+	const T *GetPtr(void) const
+	{
+		return &boost::get<T>(m_Value);
+	}
+
 private:
 	boost::variant<boost::blank, double, bool, String, Object::Ptr> m_Value;
 };