sed <a href="dart-core/Set-class.html">Set</a> may change its iteration order completely
when adding a new element to the set.</p>
<p>Modifying the underlying collection after creating the new iterator
may cause an error the next time <a href="dart-core/Iterator/moveNext.html">Iterator.moveNext</a> is called
on that iterator.
Any <em>modifiable</em> iterable class should specify which operations will
break iteration.</p>
        </section>
                <section class="summary source-code" id="source">
  