From 07a1d5f0273fdcce5ec7ec3cba9a6db232d9124b Mon Sep 17 00:00:00 2001
From: The 8472 <git@infinite-source.de>
Date: Mon, 28 Aug 2023 14:35:51 +0200
Subject: [PATCH] reduce indirection in for_each specialization

---
 library/core/src/iter/adapters/take.rs | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/library/core/src/iter/adapters/take.rs b/library/core/src/iter/adapters/take.rs
index 70252e075b9..c1d8cc4ff57 100644
--- a/library/core/src/iter/adapters/take.rs
+++ b/library/core/src/iter/adapters/take.rs
@@ -303,13 +303,12 @@ fn spec_fold<B, F>(mut self, init: B, mut f: F) -> B
     }
 
     #[inline]
-    fn spec_for_each<F: FnMut(Self::Item)>(self, f: F) {
-        // Based on the the Iterator trait default impl.
-        #[inline]
-        fn call<T>(mut f: impl FnMut(T)) -> impl FnMut((), T) {
-            move |(), item| f(item)
+    fn spec_for_each<F: FnMut(Self::Item)>(mut self, mut f: F) {
+        let end = self.n.min(self.iter.size());
+        for i in 0..end {
+            // SAFETY: i < end <= self.iter.size() and we discard the iterator at the end
+            let val = unsafe { self.iter.__iterator_get_unchecked(i) };
+            f(val);
         }
-
-        self.spec_fold((), call(f));
     }
 }