Implement the new fields for fixed width area.

src/compare/util.rs

@@ -139,7 +139,7 @@ fn assert_post_blank<'b, 's, S: StandardProperties<'s> + ?Sized>(
         .post_blank
         .ok_or("Token should have a post-blank.")?;
     if rust_post_blank as usize != emacs_post_blank {
-        Err(format!("Rust post-blank (in chars) {rust_post_blank} does not match emacs post-blank ({emacs_post_blank})", rust_post_blank = rust_post_blank, emacs_post_blank = emacs_post_blank))?;
+        Err(format!("Rust post-blank {rust_post_blank} does not match emacs post-blank ({emacs_post_blank})", rust_post_blank = rust_post_blank, emacs_post_blank = emacs_post_blank))?;
     }
 
     Ok(())

src/parser/fixed_width_area.rs

@@ -41,7 +41,7 @@ where
     let (remaining, mut remaining_lines) =
         many0(preceded(not(exit_matcher), fixed_width_area_line_matcher))(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 mut value = Vec::with_capacity(remaining_lines.len() + 1);
@@ -66,6 +66,7 @@ where
                 affiliated_keywords,
             ),
             value,
+            post_blank: post_blank.map(Into::<&str>::into),
         },
     ))
 }

src/types/lesser_element.rs

@@ -148,6 +148,7 @@ pub struct FixedWidthArea<'s> {
     pub source: &'s str,
     pub affiliated_keywords: AffiliatedKeywords<'s>,
     pub value: Vec<&'s str>,
+    pub post_blank: Option<&'s str>,
 }
 
 #[derive(Debug)]
@@ -403,11 +404,15 @@ impl<'s> StandardProperties<'s> for FixedWidthArea<'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.")
     }
 }