fix: Add None case for finding max line number

Author: chengr4

Diff for: src/renderer/display_list.rs

@@ -72,18 +72,22 @@ impl<'a> fmt::Debug for DisplayList<'a> {
 
 impl<'a> Display for DisplayList<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let max_lineno = self.body.iter().fold(0, |max, set| {
+        let max_lineno = self.body.iter().fold(None, |max, set| {
             set.display_lines.iter().fold(max, |max, line| match line {
-                DisplayLine::Source { lineno, .. } => cmp::max(lineno.unwrap_or(0), max),
+                DisplayLine::Source { lineno, .. } => match (max, lineno) {
+                    (Some(max), Some(lineno)) => Some(cmp::max(max, *lineno)),
+                    (Some(max), None) => Some(max),
+                    (None, Some(lineno)) => Some(*lineno),
+                    (None, None) => None,
+                },
                 _ => max,
             })
         });
-        let lineno_width = if max_lineno == 0 {
-            1
-        } else if self.anonymized_line_numbers {
-            ANONYMIZED_LINE_NUM.len()
-        } else {
-            ((max_lineno as f64).log10().floor() as usize) + 1
+        let lineno_width = match max_lineno {
+            None => 0,
+            Some(0) => 1,
+            Some(_max) if self.anonymized_line_numbers => ANONYMIZED_LINE_NUM.len(),
+            Some(max) => (max as f64).log10().floor() as usize + 1,
         };
 
         let multiline_depth = self.body.iter().fold(0, |max, set| {