="desc markdown">
      <p>Adapts <code>source</code> to be a <code>List&lt;T&gt;</code>.</p>
<p>Any time the list would produce an element that is not a <code>T</code>,
the element access will throw.</p>
<p>Any time a <code>T</code> value is attempted stored into the adapted list,
the store will throw unless the value is also an instance of <code>S</code>.</p>
<p>If all accessed elements of <code>source</code> are actually instances of <code>T</code>,
and if all elements stored into the returned list are a