Simplify EmitterWriter::get_max_line_num

Author: AnthonyMikh

src/librustc_errors/emitter.rs

@@ -1022,15 +1022,11 @@ impl EmitterWriter {
     }
 
     fn get_max_line_num(&mut self, span: &MultiSpan, children: &[SubDiagnostic]) -> usize {
-
         let primary = self.get_multispan_max_line_num(span);
-        let mut max = primary;
-
-        for sub in children {
-            let sub_result = self.get_multispan_max_line_num(&sub.span);
-            max = std::cmp::max(sub_result, max);
-        }
-        max
+        children.iter()
+            .map(|sub| self.get_multispan_max_line_num(&sub.span))
+            .max()
+            .unwrap_or(primary)
     }
 
     /// Adds a left margin to every line but the first, given a padding length and the label being