Throw an exception on failure

dom.bs

@@ -5037,13 +5037,22 @@ return the result of <a>pre-removing</a> <var>child</var> from <a>this</a>.
 method steps are:
 
 <ol>
- <li><p>Let <var>perform state-preserving atomic move</var> be true if <a>this</a> is
- <a>connected</a>, <var>node</var> is <a>connected</a>, <a>this</a>'s <a for=Node>node
- document</a> is <a>fully active</a>, and <a>this</a>'s <a for=/>root</a> is the same as
- <var>node</var>'s <a for=/>root</a>.</p></li>.
+ <li><p>If any of the following conditions are false:</p>
 
- <li><p>If <var>perform state-preserving atomic move</var> is true, then set <a>this</a>'s <a
- for=Node>node document</a>'s <a>state-preserving atomic move in progress</a> to true.</p></li>
+  <ul>
+   <li><p><a>this</a> is <a>connected</a>;</p></li>
+
+   <li><p><var>node</var> is <a>connected</a>;</p></li>
+
+   <li><p><a>this</a>'s <a for=Node>node document</a> is <a>fully active</a>; or</p></li>
+
+   <li><p><a>this</a>'s <a for=/>root</a> is the same as <var>node</var>'s <a for=/>root</a>,</p></li>
+  </ul>
+
+ <li><p>then <a>throw</a> "{{HierarchyRequestError!!exception}}" {{DOMException}}.</p>
+
+ <li><p>Set <a>this</a>'s <a for=Node>node document</a>'s
+ <a>state-preserving atomic move in progress</a> to true.</p></li>
 
  <li><p>Let <var>return node</var> be the result of <a>pre-inserting</a> <var>node</var> into
  <a>this</a> before <var>child</var>.</p></li>