cpp/experimental/unique resource/operator=

Move assignment operator. Replaces the managed resource and the deleter with 's.

Formally, let be the type of stored resource handle:
 * First, calls to dispose the currently owned resource, if any.
 * Then assigns the stored resource handle and the deleter with 's. is applied to the stored resource handle or the deleter of  if  or  is  respectively. Assignment of the stored resource handle is executed first, unless  is  and  is.
 * Finally, sets to own the resource if and only if  owned it before assignment, and  not to own the resource.

If is,  shall satisfy the  requirements; otherwise  shall satisfy the  requirements. If is,  shall satisfy the  requirements; otherwise  shall satisfy the  requirements. Failing to satisfy above requirements results in undefined behavior.

Exceptions
Any exception thrown in copy-assignment.