refactor(tree): remove unused constants, debug prints, and imports

- Removed unused constants and redundant imports.
- Eliminated debug print statements from the `search` module.
- Added `#[allow(dead_code)]` annotations to suppress warnings for unused functions.
- Made `Tree` and `as_subtree_mut` public

src/tree.rs

@@ -18,13 +18,6 @@ use core::{marker::PhantomData, mem::MaybeUninit, ptr::NonNull};
 mod marker {
     use core::marker::PhantomData;
 
-    #[derive(Debug)]
-    pub struct LeafOrInternal;
-    #[derive(Debug)]
-    pub struct Leaf;
-    #[derive(Debug)]
-    pub struct Internal;
-
     #[derive(Debug)]
     pub struct Edge;
     #[derive(Debug)]
@@ -58,8 +51,6 @@ mod marker {
     impl BorrowType for DormantMut {}
 }
 
-const CAPACITY: usize = 16;
-
 #[derive(Debug)]
 struct LeafNode<K, V> {
     parent: Option<BoxedNode<K, V>>,
@@ -163,6 +154,7 @@ impl<BorrowType: marker::BorrowType, K, V> NodeRef<BorrowType, K, V> {
     ///
     /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
     /// both, upon success, do nothing.
+    #[allow(dead_code)]
     pub(super) fn ascend(self) -> Result<Handle<NodeRef<BorrowType, K, V>, marker::Edge>, Self> {
         const {
             assert!(BorrowType::TRAVERSAL_PERMIT);
@@ -220,6 +212,7 @@ impl<'a, K, V, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V>, HandleType> {
     /// dangerous.
     ///
     /// For details, see `NodeRef::reborrow_mut`.
+    #[allow(dead_code)]
     pub(super) unsafe fn reborrow_mut(
         &mut self,
     ) -> Handle<NodeRef<marker::Mut<'_>, K, V>, HandleType> {
@@ -266,6 +259,7 @@ impl<K, V> NodeRef<marker::Owned, K, V> {
     }
 
     /// Slightly mutably borrows the owned root node.
+    #[allow(dead_code)]
     pub(super) fn borrow_valmut(&mut self) -> NodeRef<marker::ValMut<'_>, K, V> {
         NodeRef {
             node: self.node,
@@ -275,6 +269,7 @@ impl<K, V> NodeRef<marker::Owned, K, V> {
 
     /// Irreversibly transitions to a reference that permits traversal and offers
     /// destructive methods and little else.
+    #[allow(dead_code)]
     pub(super) fn into_dying(self) -> NodeRef<marker::Dying, K, V> {
         NodeRef {
             node: self.node,
@@ -471,6 +466,7 @@ impl<BorrowType, K, V> NodeRef<BorrowType, K, V> {
         this.node.as_ptr()
     }
 
+    #[allow(dead_code)]
     fn as_leaf(&self) -> &LeafNode<K, V> {
         // SAFETY: the static node type is `Leaf`.
         unsafe { &*Self::as_leaf_ptr(self) }
@@ -540,6 +536,7 @@ pub(super) enum ForceResult<Node> {
     Internal(Node),
 }
 
+#[allow(dead_code)]
 impl<BorrowType, K, V, HandleType> Handle<NodeRef<BorrowType, K, V>, HandleType> {
     fn force(self) -> ForceResult<Handle<NodeRef<BorrowType, K, V>, HandleType>> {
         match self.node.force() {
@@ -645,6 +642,7 @@ impl<K, V> NodeRef<marker::Owned, K, V> {
     }
 }
 
+#[allow(dead_code)]
 impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V>, marker::Edge> {
     /// Converts this edge handle into a value handle.
     /// IMPORTANT: this handle points to the value of the node, not the edge.
@@ -778,17 +776,14 @@ mod search {
                 match key.cmp(k.borrow()) {
                     Ordering::Greater => {}
                     Ordering::Equal => {
-                        std::eprintln!("found key at index {}", start_index + offset);
                         return IndexResult::Edge(start_index + offset);
                     }
                     Ordering::Less => {
-                        std::eprintln!("insert key at index {}", start_index + offset);
                         return IndexResult::Insert(start_index + offset);
                     }
                 }
             }
 
-            std::eprintln!("push_back key at index {}", keys.len());
             IndexResult::Insert(keys.len())
         }
     }
@@ -796,7 +791,6 @@ mod search {
     #[cfg(test)]
     mod tests {
         use super::super::Tree;
-        use super::*;
 
         fn insert_and_dbg<'a>(
             tree: &'a mut Tree<char, &'static str>,
@@ -837,9 +831,7 @@ enum HandleOrTree<'a, BorrowType, K, V, HandleType> {
 mod entry {
     use core::marker::PhantomData;
 
-    use crate::tree::LeafNode;
-
-    use super::{Handle, NodeRef, Tree, borrow::DormantMutRef, marker};
+    use super::{Handle, NodeRef, marker};
 
     pub enum Entry<'a, Q: 'a, K: 'a, V: 'a>
     where
@@ -1067,6 +1059,8 @@ mod subtree {
 }
 
 mod borrow {
+    #![allow(dead_code)]
+
     use core::{marker::PhantomData, ptr::NonNull};
 
     /// Models a reborrow of some unique reference, when you know that the reborrow
@@ -1142,7 +1136,7 @@ mod borrow {
 
 type Root<K, V> = NodeRef<marker::Owned, K, V>;
 
-struct Tree<K, V> {
+pub struct Tree<K, V> {
     root: Option<Root<K, V>>,
     _marker: PhantomData<alloc::boxed::Box<(K, V)>>,
 }
@@ -1263,7 +1257,7 @@ impl<K, V> Tree<K, V>
 where
     K: Ord,
 {
-    fn as_subtree_mut<'a>(&'a mut self) -> Option<subtree::Subtree<K, V, marker::Mut<'a>>> {
+    pub fn as_subtree_mut<'a>(&'a mut self) -> Option<subtree::Subtree<K, V, marker::Mut<'a>>> {
         let root = self.root.as_mut()?.borrow_mut().dormant();
 
         Some(subtree::Subtree {