wpautop bad code

[jim5471]

post content

<a href="document.htm"><div>Text</div></a>

generated markup - note wrong HTML

<p><a href="document.htm"></p>
<div>Text</div>
<p></a></p>

related: #40135

[jim5471]

Similar result Post content

<a href="document.htm"><span>Text</span></a>

generated markup

<p><a href="document.htm"><span>Text</span></a></p>
<p><span><img src="image.png" alt="thumb"></p>

[noisysocks]

I can reproduce this. Possibly same root cause as #27350.