From 5b12d906bb66d308fb3e94d6d79e076fa87c7f7c Mon Sep 17 00:00:00 2001
From: Slanterns <slanterns.w@gmail.com>
Date: Tue, 22 Oct 2024 01:08:15 -0700
Subject: [PATCH] optimize `Rc<T>::default`

---
 library/alloc/src/rc.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index e98ae7c31ad..582d850e14b 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -2312,7 +2312,16 @@ impl<T: Default> Default for Rc<T> {
     /// ```
     #[inline]
     fn default() -> Rc<T> {
-        Rc::new(Default::default())
+        unsafe {
+            Self::from_inner(
+                Box::leak(Box::write(Box::new_uninit(), RcInner {
+                    strong: Cell::new(1),
+                    weak: Cell::new(1),
+                    value: T::default(),
+                }))
+                .into(),
+            )
+        }
     }
 }