From f288bcb53caeb847b7fea5c34f83dccb589538ff Mon Sep 17 00:00:00 2001
From: Amin Yahyaabadi <aminyahyaabadi74@gmail.com>
Date: Thu, 30 Sep 2021 17:02:06 -0500
Subject: [PATCH 1/2] 1. [feature] add parent_mut method to Node

---
 src/node.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/node.rs b/src/node.rs
index 386f794..47f85ad 100644
--- a/src/node.rs
+++ b/src/node.rs
@@ -189,6 +189,24 @@ impl<T> Node<T> {
         None
     }
 
+    /// Returns a mutable reference to the parent node of this node,
+    /// or None if it is the root node.
+    /// Also see the `parent` method.
+    pub fn parent_mut( &self ) -> Option<&mut Node<T>> {
+        let mut node = self.non_null();
+        unsafe {
+            while let Some( parent ) = node.as_ref().up {
+                if parent.as_ref().is_forest() {
+                    node = parent;
+                } else {
+                    return Some( &mut *parent.as_ptr() );
+                }
+            }
+        }
+        None
+    }
+
+
     /// Inserts sib tree before `self`.
     /// The newly inserted node will not be iterated over by the currently running iterator.
     ///

From f5be99c47c63f8a559e6d7c9aa4c19aa3d9c3d2c Mon Sep 17 00:00:00 2001
From: Amin Yahyaabadi <aminyahyaabadi74@gmail.com>
Date: Sat, 2 Oct 2021 22:14:52 -0500
Subject: [PATCH 2/2] 1. [fix] mark parent_mut as unsafe fn

---
 src/node.rs | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/node.rs b/src/node.rs
index 47f85ad..063bd45 100644
--- a/src/node.rs
+++ b/src/node.rs
@@ -190,17 +190,15 @@ impl<T> Node<T> {
     }
 
     /// Returns a mutable reference to the parent node of this node,
-    /// or None if it is the root node.
+    /// or None if it is the root node. Ensure that there is only one reference to the returned value.
     /// Also see the `parent` method.
-    pub fn parent_mut( &self ) -> Option<&mut Node<T>> {
+    pub unsafe fn parent_mut( &self ) -> Option<&mut Node<T>> {
         let mut node = self.non_null();
-        unsafe {
-            while let Some( parent ) = node.as_ref().up {
-                if parent.as_ref().is_forest() {
-                    node = parent;
-                } else {
-                    return Some( &mut *parent.as_ptr() );
-                }
+        while let Some( parent ) = node.as_ref().up {
+            if parent.as_ref().is_forest() {
+                node = parent;
+            } else {
+                return Some( &mut *parent.as_ptr() );
             }
         }
         None