otherwise the type assertion is invalid since it is not possible for <code>x</code>
to store a value of type <code>T</code>.
If <code>T</code> is an interface type, <code>x.(T)</code> asserts that the dynamic type
of <code>x</code> <a href="#Implementing_an_interface">implements</a> the interface <code>T</code>.
</p>
<p>
If the type assertion holds, the value of the expression is the value