title: In Dart, does `List.unmodifiable` create an unmodifiable view, or a whole new independent list?
body: <ol>
  <li>In Dart, do <code>List.unmodifiable(someList)</code> and <code>Map.unmodifiable(someMap)</code> create an unmodifiable <strong>view</strong>, or a whole new independent list/map? I am guessing it's a new independent list, but I must be sure.
  <ul>
  <li>If it's a view, modifications to the original list will modify the now not so unmodifiable list, but sometimes you are just discarding the original anyway, and creating a view is much faster.</li>
  </ul>
  </li>
  <li>And, in case they create independent lists/maps, is there some way to create an unmodifiable view, for performance purposes?
  <ul>
  <li><strong>Update</strong>: Ok, I have answered my own question number 2, by finding this: <a href="https://api.dartlang.org/stable/1.23.0/dart-collection/UnmodifiableListView-class.html" rel="nofollow noreferrer"><code>UnmodifiableListView&lt;E&gt;</code> Docs</a>. But I still need to know the answer to the other questions.</li>
  </ul>
  </li>
  <li>What's the Big O for creating a dart list from another one, including the one created by <code>List.unmodifiable(someList)</code>? For example, this is the info for Java collections: <a href="https://gist.github.com/FedericoPonzi/8d5094dbae33cbb94536a73f62d1c1a0" rel="nofollow noreferrer">Big O for Java Collections</a>.</li>
  </ol>