Returning an argument passed by rvalue reference

If I have a class A and functions A f(A &&a) { doSomething(a); return a; } A g(A a) { doSomething(a); return a; } the copy constructor is called when returning a from f, but the move constructor is used when returning from g. However, from what I understand, f can only be passed an object that it is safe to move (either a temporary or an object marked as moveable, e.g., using std::move). Is there any example when it would not be safe to use the move constructor when returning from f? Why do we require a to have automatic storage duration? I read the answers here, but the top answer only shows that the spec should not allow moving when passing a to other functions in the function body; it does not explain why moving when returning is safe for g but not for f. Once we get to the return statement, we will not need a anymore inside f. Update 0 So I understand that temporaries are accessible until the end of the full expression. However, the behavior when returning from f still seems to go against the semantics ingrained into the language that it is safe to move a temporary or an xvalue. For example, if you call g(A()), the temporary is moved into the argument for g even though there could be references to the temporary stored somewhere. The same happens if we call g with an xvalue. Since only temporaries and xvalues bind to rvalue references, it seems like to be consistent about the semantics we should still move a when returning from f, since we know a was passed either a temporary or an xvalue.