Use map, sum in Subtree::coount instead of fold

crates/ra_tt/src/lib.rs

@@ -153,11 +153,15 @@ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 impl Subtree {
     /// Count the number of tokens recursively
     pub fn count(&self) -> usize {
-        self.token_trees.iter().fold(self.token_trees.len(), |acc, c| {
-            acc + match c {
+        let children_count = self
+            .token_trees
+            .iter()
+            .map(|c| match c {
                 TokenTree::Subtree(c) => c.count(),
                 _ => 0,
-            }
-        })
+            })
+            .sum::<usize>();
+
+        self.token_trees.len() + children_count
     }
 }