Some optimizations (3)

Cargo.toml

@@ -26,6 +26,7 @@ clap = { version = "3.1.8", features = ["cargo", "env", "wrap_help"] }
 itertools = "0.10.1"
 typed-arena = "2.0.1"
 rustc-hash = "1.1.0"
+hashbrown = "0.12.3"
 strsim = "0.10.0"
 lazy_static = "1.4.0"
 atty = "0.2.14"

src/diff/changes.rs

@@ -26,27 +26,32 @@ impl<'a> ChangeMap<'a> {
     pub fn get(&self, node: &Syntax<'a>) -> Option<ChangeKind<'a>> {
         self.changes.get(&node.id()).copied()
     }
+
+    pub fn reserve(&mut self, additional: usize) {
+        self.changes.reserve(additional);
+    }
 }
 
 pub fn insert_deep_unchanged<'a>(
-    node: &'a Syntax<'a>,
-    opposite_node: &'a Syntax<'a>,
+    lhs: &'a Syntax<'a>,
+    rhs: &'a Syntax<'a>,
     change_map: &mut ChangeMap<'a>,
 ) {
-    change_map.insert(node, ChangeKind::Unchanged(opposite_node));
+    change_map.insert(lhs, ChangeKind::Unchanged(rhs));
+    change_map.insert(rhs, ChangeKind::Unchanged(lhs));
 
-    match (node, opposite_node) {
+    match (lhs, rhs) {
         (
             Syntax::List {
-                children: node_children,
+                children: lhs_children,
                 ..
             },
             Syntax::List {
-                children: opposite_children,
+                children: rhs_children,
                 ..
             },
         ) => {
-            for (child, opposite_child) in node_children.iter().zip(opposite_children) {
+            for (child, opposite_child) in lhs_children.iter().zip(rhs_children) {
                 insert_deep_unchanged(child, opposite_child, change_map);
             }
         }