refactored counting functions to use `std::iter::successors`

src/diff/dijkstra.rs

@@ -156,33 +156,20 @@ fn edge_between<'s, 'v>(before: &Vertex<'s, 'v>, after: &Vertex<'s, 'v>) -> Edge
 
 /// What is the total number of AST nodes?
 fn node_count(root: Option<&Syntax>) -> u32 {
-    let mut node = root;
-    let mut count = 0;
-    while let Some(current_node) = node {
-        let current_count = match current_node {
+    let iter = std::iter::successors(root, |node| node.next_sibling());
+
+    iter.map(|node| match node {
         Syntax::List {
             num_descendants, ..
         } => *num_descendants,
         Syntax::Atom { .. } => 1,
-        };
-        count += current_count;
-
-        node = current_node.next_sibling();
-    }
-
-    count
+    })
+    .sum::<u32>()
 }
 
 /// How many top-level AST nodes do we have?
 fn tree_count(root: Option<&Syntax>) -> u32 {
-    let mut node = root;
-    let mut count = 0;
-    while let Some(current_node) = node {
-        count += 1;
-        node = current_node.next_sibling();
-    }
-
-    count
+    std::iter::successors(root, |node| node.next_sibling()).count() as _
 }
 
 pub(crate) fn mark_syntax<'a>(

src/diff/stack.rs

@@ -39,13 +39,7 @@ impl<'b, T> Stack<'b, T> {
 
     // O(n)
     pub(crate) fn size(&self) -> usize {
-        let mut count = 0;
-        let mut node = &self.head;
-        while let Some(next) = node {
-            count += 1;
-            node = &next.next;
-        }
-        count
+        std::iter::successors(self.head, |&n| n.next).count()
     }
 
     pub(crate) fn is_empty(&self) -> bool {

src/parse/guess_language.rs

@@ -569,7 +569,7 @@ fn from_emacs_mode_header(src: &str) -> Option<Language> {
             "yaml" => Yaml,
             "zig" => Zig,
             _ => continue,
-        })
+        });
     }
 
     None