Forward declare a subclass that inherits from a class in different namespace
<p>I don't understand why this fails to compile:</p>

<pre><code>#include &lt;SomeType.h&gt; // has a namespace called SomeNamespace

class MyApplication;

int main(...)
{
...
MyApplication application;
...
}

class MyApplication : public SomeNamespace::SomeType {
...
};
</code></pre>

<p>As it stands I'm getting this error from g++ (Ubuntu 4.4.3-4ubuntu5) 4.4.3</p>

<pre><code>../fix-protocol/main.cpp:44: error: aggregate ‘MyApplication application’ has incomplete type and cannot be defined
</code></pre>
