From e7fe2dfef253c462699783e7b2b297827f7440a7 Mon Sep 17 00:00:00 2001
From: inquisitivecrystal
 <22333129+inquisitivecrystal@users.noreply.github.com>
Date: Tue, 20 Jul 2021 15:40:30 -0700
Subject: [PATCH] Use hashbrown's `extend_reserve()` in `HashMap`

---
 library/std/src/collections/hash/map.rs | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index fac285c96f00d..c07555c910114 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -2786,15 +2786,7 @@ where
 
     #[inline]
     fn extend_reserve(&mut self, additional: usize) {
-        // self.base.extend_reserve(additional);
-        // FIXME: hashbrown should implement this method.
-        // But until then, use the same reservation logic:
-
-        // Reserve the entire hint lower bound if the map is empty.
-        // Otherwise reserve half the hint (rounded up), so the map
-        // will only resize twice in the worst case.
-        let reserve = if self.is_empty() { additional } else { (additional + 1) / 2 };
-        self.base.reserve(reserve);
+        self.base.extend_reserve(additional);
     }
 }