c++ - Move assignable class containing vector<unique_ptr<T>> -

the class foo has rvalue reference constructor moves contained vector of unique_ptr's why following code give following error, both or without std::move on foo() in main?

error 1 error c2280: 'std::unique_ptr> &std::unique_ptr<_ty,std::default_delete<_ty>>::operator =(const std::unique_ptr<_ty,std::default_delete<_ty>> &)' : attempting reference deleted function

class foo{ public:     foo(){      }     foo(foo&& other) :         m_bar(std::move(other.m_bar))     {};      std::vector<std::unique_ptr<something>> m_bar; };  int main(int argc, char* argv[]) {     foo f;     f = std::move(foo());     return 0; } 

this:

 f = std::move(foo()); 

doesn't call move constructor. calls move assignment operator. furthermore, it's redundant, since foo() rvalue that's equivalent to:

f = foo(); 

since declared move constructor, move assignment operator isn't declared - there isn't one. either have provide one:

foo& operator=(foo&& other) {     m_bar = std::move(other.m_bar);     return *this; } 

or, since members implement move operations themselves, delete move constructor , rely on compiler-generated implicit move constructor , move assignment.