<code>S1</code> and <code>S2</code> may have or share.
</p>

<p>
Every type that is a member of the type set of an interface implements that interface.
Any given type may implement several distinct interfaces.
For instance, all types implement the <i>empty interface</i> which stands for the set
of all (non-interface) types:
</p>

<pre>
interface{}
</pre>

<p>