From 0191b93db9f56fa58f520f1f5c5f8437edf836c1 Mon Sep 17 00:00:00 2001
From: Kornel <kornel@geekhood.net>
Date: Fri, 20 Oct 2023 03:29:46 +0100
Subject: [PATCH] Update library/alloc/src/raw_vec.rs

Co-authored-by: scottmcm <scottmcm@users.noreply.github.com>
---
 library/alloc/src/raw_vec.rs | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/library/alloc/src/raw_vec.rs b/library/alloc/src/raw_vec.rs
index bc994694ad7e..d335ac80d189 100644
--- a/library/alloc/src/raw_vec.rs
+++ b/library/alloc/src/raw_vec.rs
@@ -291,10 +291,14 @@ impl<T, A: Allocator> RawVec<T, A> {
 
         if self.needs_to_grow(len, additional) {
             do_reserve_and_handle(self, len, additional);
-            unsafe {
-                // Inform the optimizer that the reservation has succeeded
-                core::intrinsics::assume(!self.needs_to_grow(len, additional));
-            }
+        }
+
+        // SAFETY: The call to `do_reserve_and_handle` ensured this
+        // (or it panicked) and thus the addition cannot overflow.
+        unsafe {
+            // Inform the optimizer that the reservation has succeeded
+            let min_cap = len.unchecked_add(additional);
+            core::intrinsics::assume(self.cap >= min_cap);
         }
     }