Fix to prefer flow over definitions, setext headings

An undocumented part of CommonMark is how to deal with things in definition
labels or definition titles (which both can span multiple lines).
Can flow (or containers?) interrupt them?
They can according to the `cmark` reference parser, so this was implemented here.

This adds a new `Content` content type, which houses zero or more definitions,
and then zero-or-one paragraphs.
Content can be followed by a setext heading underline, which either turns
into a setext heading when the content ends in a paragraph, or turns into
the start of the following paragraph when it is followed by content that
starts with a paragraph, or turns into a stray paragraph.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/construct/label_end.rs b/src/construct/label_end.rs
index ce1c295..95b9a27 100644
--- a/src/construct/label_end.rs
+++ b/src/construct/label_end.rs
@@ -183,6 +183,7 @@ use crate::construct::partial_space_or_tab_eol::space_or_tab_eol;
 use crate::event::{Event, Kind, Name};
 use crate::resolve::Name as ResolveName;
 use crate::state::{Name as StateName, State};
+use crate::subtokenize::Subresult;
 use crate::tokenizer::{Label, LabelKind, LabelStart, Tokenizer};
 use crate::util::{
     constant::RESOURCE_DESTINATION_BALANCE_MAX,
@@ -660,7 +661,7 @@ pub fn reference_collapsed_open(tokenizer: &mut Tokenizer) -> State {
 ///
 /// This turns matching label starts and label ends into links, images, and
 /// footnotes, and turns unmatched label starts back into data.
-pub fn resolve(tokenizer: &mut Tokenizer) {
+pub fn resolve(tokenizer: &mut Tokenizer) -> Result<Option<Subresult>, String> {
     // Inject labels.
     let labels = tokenizer.tokenize_state.labels.split_off(0);
     inject_labels(tokenizer, &labels);
@@ -671,6 +672,8 @@ pub fn resolve(tokenizer: &mut Tokenizer) {
     mark_as_data(tokenizer, &starts);
 
     tokenizer.map.consume(&mut tokenizer.events);
+
+    Ok(None)
 }
 
 /// Inject links/images/footnotes.