Implement the new fields for LaTeX environment.

src/parser/latex_environment.rs

@@ -57,7 +57,7 @@ where
     let (remaining, _end) = latex_environment_end_specialized(&parser_context, remaining)?;
     let value_end = remaining;
 
-    let (remaining, _trailing_ws) =
+    let (remaining, post_blank) =
         maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;
     let source = get_consumed(input, remaining);
     let value = get_consumed(value_start, value_end);
@@ -70,6 +70,7 @@ where
                 affiliated_keywords,
             ),
             value: value.into(),
+            post_blank: post_blank.map(Into::<&str>::into),
         },
     ))
 }

src/types/lesser_element.rs

@@ -173,6 +173,7 @@ pub struct LatexEnvironment<'s> {
     pub source: &'s str,
     pub affiliated_keywords: AffiliatedKeywords<'s>,
     pub value: &'s str,
+    pub post_blank: Option<&'s str>,
 }
 
 /// A line number used in switches to lesser blocks.
@@ -425,11 +426,15 @@ impl<'s> StandardProperties<'s> for LatexEnvironment<'s> {
     }
 
     fn get_contents<'b>(&'b self) -> Option<&'s str> {
-        todo!()
+        None
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        todo!()
+        self.post_blank
+            .map(|text| text.lines().count())
+            .unwrap_or(0)
+            .try_into()
+            .expect("Too much post-blank to fit into a PostBlank.")
     }
 }