EXP63-CPP. Do not rely on the value of a moved-from object

Many types, including user-defined types and types provided by the Standard Template Library, support move semantics. Except in rare circumstances, an object of a type that supports move operations (move initialization or move assignment) will be left in a valid, but unspecified state after the object's value has been moved.

Passing an object as a function argument that binds to an rvalue reference parameter, including via implicit function call syntax such as move assignment or move construction, moves the object's state into another object. Upon return from such a function call, the object that was bound as an rvalue reference parameter is considered to be in the moved-from state. Once an object is in the moved-from state, the only operations that may be safely performed on that object instance are ones for which the operation has no preconditions, because it is unknown whether the unspecified state of the object will satis