title: When I use positional-only arguments with annotations in Python 3.8, I get a symtable that seems incorrect
body: <p>Python 3.8 has a new syntax feature for <a href="https://www.python.org/dev/peps/pep-0570/" rel="nofollow noreferrer">positional-only function arguments</a>. When I use this feature in conjunction with annotations, and produce a symbol table for the code, a symbol seems to be missing.</p>
  
  <p>Without positional-only args:</p>
  
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; import symtable
  &gt;&gt;&gt; symtable.symtable('def f(x: y): pass', '?', 'exec').get_symbols()
  [&lt;symbol 'f'&gt;, &lt;symbol 'y'&gt;]
  </code></pre>
  
  <p>This is expected. <code>f</code> and <code>y</code> are symbols in the global scope. Now I'm adding a <code>/</code> to mark the argument positional-only:</p>
  
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; symtable.symtable('def f(x: y, /): pass', '?', 'exec').get_symbols()
  [&lt;symbol 'f'&gt;]
  </code></pre>
  
  <p><strong>This seems wrong.</strong> Symbol <code>y</code> is missing, although it's still an annotation of <code>x</code> and should therefore still be present in the root symtable. Is this an internal bug, or am I missing side-effects of this new feature?</p>
  
  <p>(I'm using CPython 3.8.0.)</p>