why does this HTML block start and end on the same line?

[step-]

Why is the HTML block (spec 4.6) closed on the same line when https://github.com/commonmark/commonmark-spec/blob/d5706b9553d4665ca730524323d484880440186c/spec.txt#L2368 says that

[An HTML block] ends with the first subsequent line that meets a matching end condition. (emphasis mine)

cmark << EOF
<!-- comment --> 0
1
-->
2
EOF

<!-- raw HTML omitted -->
<p>1
--&gt;
2
EOF</p>

I think cmark parses the comment as an HTML block. It couldn't be a raw HTML comment (spec 6.6) otherwise "0" would surface inside a <p>. So it seems that, contrary to the specification, the HTML block ends on the same line where it starts, instead of ending between "1" and "2".

[jgm]

I think maybe the word "subsequent" is misplaced. There can definitely be HTML blocks that start and end on the same line, e.g.

<div></div>

[step-]

Should I open an issue about "subsequent" in the specification repo?

[jgm]

Yes please.