Why does this need an explicit std::move?

Question

Let\'s say I got a Foo class containing an std::vector constructed from std::unique_ptr objects of another class, Bar.

Answer 1

bar is defined as an rvalue-reference, but its value-category is an lvalue. This is so because the object has a name. If it has a name, it's an lvalue. Therefore an explicit std::move is necessary because the intention is to get rid of the name and return an xvalue (eXpiring-rvalue).